Access LOMAX vs BAKFlip MX4: The Lift-Off Cover Wins on Water

Fold a BAKFlip MX4 and its panels stand against the cab, so the whole bed opens with the cover still on the truck. Fold an Access LOMAX and the rear panels stack onto the front one over the first third of the bed; for the rest, you lift the cover off, which takes about a minute and no tools. Most of the other differences follow from how each one sits. The MX4 rides down inside the bed rails and carries water to drain tubes. The LOMAX sits on top of the rails, less than half an inch above the bed, with no drains at all.

The LOMAX scores ahead on all three counts, by enough to name it the winner. Its owners mostly describe a dry bed or a few drops at the tailgate, while most MX4 owners who mention water describe leaks, so we rate leak risk moderate on the LOMAX and high on the MX4. It also cost a little less on all four beds where we confirmed both on Amazon. The MX4 answers with 5 years of warranty for the original buyer against the LOMAX's 3 years of parts-only coverage, and with confirmed listings for the Ram 1500 and the Silverado and Sierra 1500, where we couldn't confirm a LOMAX.

Our pick is the LOMAX. It keeps the bed drier, cost less wherever we compared the same bed, needs no drain tubes and comes off whole when you need the front of the bed. Buy the MX4 instead if you haul full-length loads every week and want the cover on while you do, if you drive a Ram 1500 or a GM half-ton, or if you want a rack on T-slot rails (the MX4 TS) or a lift assist for heavy, wet winters (the MX4 EZ-Lift).

Lift it off or fold it to the cab

You'll feel this difference every time you load the truck. The MX4 folds forward on prop rods and leans back toward the rear window, and you can drive with it open. The LOMAX's stack clips down over the front of the bed. Agri-Cover doesn't publish panel lengths. On a Gen14 F-150 short bed, which BAK and UnderCover list at 67.1 in, three panels of about equal length would stack over roughly the first 22 in and leave about 45 in open. For a load that needs that front section, unclip the two safety straps, pull the tab on the front panel, slide the cover back and lift it off. The rails stay on the truck, so it goes back on the same way.

The rear window is where the trade flips. The LOMAX stack leaves the glass clear. The MX4's leans toward it: RealTruck says the third brake light stays clear, and on an F-150 the stack clears the bed camera, but on a Colorado it blocks the view out the back entirely, and on a Tacoma it pressed on the rear camera. That lean is also what makes room for tall cargo. A Ram owner keeps an MX4 that leaks because folding it against the glass is what makes room for an ATV.

Lifting the LOMAX off is a one-person job. Agri-Cover puts its weight at about 40 to 50 lb on one page and about 50 lb on another, and the aluminum panels have no foam core. BAK doesn't publish the MX4's weight, and in hard-winter climates its foam-core panels can take on water and get heavy to fold; RealTruck says the EZ-Lift version cuts lift force to 10.5 lb.

Not every LOMAX owner is sold on the stack. A Tacoma owner whose friend runs a BAKFlip thinks the BAKFlip has the nicer fit and finish and, for the full-bed fold, would have bought it instead.

The numbers from Agri-Cover and BAK

Every cell comes from the makers' own pages, with RealTruck's product page for the MX4:

The matching 400 lb means the same thing on both: weight spread evenly across the whole closed cover. Neither maker gives a figure for weight concentrated in one spot, and Agri-Cover's manual says to place nothing on or against the LOMAX and never to stand, sit or ride on it. Treat the rating as panel strength for snow, not a shelf. Neither cover has a keyed lock, so with either one shut the bed is as secure as your tailgate lock.

Rain, car washes and the corners that drip

The LOMAX is the drier cover, and most of its lead comes from here. A typical LOMAX keeps the bed dry or lets in a few drops at the tailgate end in a downpour or a car wash, with the front corners at the bulkhead next, and bad leaks are rare. MX4 owners who mention water mostly describe leaks: the front corners next to the rear window take it first, then the tailgate end, then the side rails, with hard rain the usual trigger. Agri-Cover's own manual says the LOMAX doesn't keep all moisture and dust out, and BAK calls some leaking normal for the MX4.

The designs explain the gap. Water lands on the MX4 and has to be carried along channels in the rails to drain tubes at the front of the bed, and with a rail even a few millimeters off, it gets past the channel. The LOMAX overlaps the bed rails with a continuous seal along each side and sheds water across its hinges, so there's no channel to miss and no tube to clog. When one of its seals doesn't seat, there's nothing to catch the water either. A Sierra owner who swapped a leaking MX4 for a LOMAX found it more water resistant right away, while allowing that the MX4's install might have been the problem.

Both can be made drier, and the MX4 asks for more work. On a LOMAX it's mostly setup: set the rails level and no higher than they need to be, put Agri-Cover's black sealant on the bed cap corners, factory holes and stake pockets, lay the front seal with its tall side toward the cab, and add a tailgate seal if the gate end drips. On an MX4, owners who got to a dry bed used silicone along the rails, weather stripping under the rail seal and at the bulkhead, a tailgate seal kit and careful front-to-back positioning, so the front seal fully overlaps the bulkhead foam. Don't count on a warranty swap to cure an MX4 that leaks, since replacements have leaked just as badly as the originals.

Drain tubes, deck rails and drilling

The LOMAX is the simpler install. Its rails clamp at four points per side with the weather strip against the inside lip of the bed, there's nothing to plumb, and Agri-Cover says one person can fit it in minutes. The MX4 clamps on with no drilling for the cover itself on most trucks, and RealTruck quotes 30 minutes or less, but each clamp has to click up into a groove in the rail before the rails sit flush, and the drain tubes have to go somewhere.

That somewhere can mean a drill. On a 4th gen Tacoma the bed's drain hole is 5/16 in and the MX4's tube is 5/8 in, so you drill or fit a barbed reducer, and some owners drill the front wall of the bed instead. If a drop-in liner covers your drain holes, plan the routing before you install. Route both tubes all the way out of the bed and keep them clear; they clog, and the hoses can pop off. Agri-Cover's clamps need no drilling; the exception we know of is its sheet for GM's CarbonPro bed, which drills six small holes through the bed cap. The install guide for your truck governs either way.

On a Tacoma, the two treat the factory rails differently. The MX4 for the 3rd gen (2016-2023) keeps the factory track system but leaves it sitting lower in the bed. The LOMAX bolts to the deck rails on brackets and leaves them where they are, though Agri-Cover warns the cover may disable or limit use of some deck rail systems. On the 4th gen (2024 on), RealTruck says the MX4 requires Toyota's deck rail system and BAK's sheet mounts the cover's rails on the factory rails where they are; Agri-Cover offers the LOMAX with or without the deck rails and bolts its brackets into the factory bed bolt locations.

For a rack, the MX4 TS adds T-slot side rails, and Agri-Cover says the LOMAX works with stake-pocket bed racks and sells it in a combo with its ADARAC Pro Series rack. For a toolbox, Agri-Cover rules out an over-the-rail box with the LOMAX, and BAK's own BAK Box no longer fits the redesigned MX4 rails.

Seals, latches and the warranty behind them

The LOMAX has the steadier record. Covers on Rams, Tundras, Tacomas and a Maverick have run three to seven years, and the weak spots show around year three or four. On a 2019 Tacoma every rubber seal had deteriorated at four years, and Agri-Cover told its owner the seals between the panels can't be replaced, though it publishes replacement instructions for the edge, front and rear seals and a hinge gap kit. On another four-year-old cover the latch area began separating from the top panel when the glue gave out. The thin panels flex a little when you lift them.

The MX4's reputation was built by earlier versions that ran five to nine years. The current Gen 3, which RealTruck re-engineered with new latches, clamps and seals, hasn't been out long enough to inherit that record, and recent covers draw complaints about rails that won't seat, clamps that don't stay tight and faults on arrival, from a broken latch to latches installed wrong at the factory. The MX4's matte top scratches easily and can dent under a snow broom, the prop rods pop out, and the plastic latch parts get brittle with age, with replacement parts slow to arrive.

The warranties run the other way. BAK backs the MX4 for 5 years for the original buyer, and the coverage doesn't transfer, so a used MX4 comes with none. Agri-Cover covers the LOMAX for 3 years from the date you receive it or the date it was made, on the truck model it was built for, and repairs or replaces defective parts only, with no labor; it issues a return authorization and pays the return freight. Keep the LOMAX's serial number, on a decal under the rear panel on the driver's side. With seals that can wear out around year four, that shorter coverage is the MX4's best argument after the fold. Whichever you buy, inspect it the day it arrives, before you install it, so a shipping claim stays simple.

Truck by truck: confirmed listings

BAK and Agri-Cover each build one cover per truck and bed, and Amazon sells them one listing per fit. We confirmed every Amazon row in the fitment tables on that listing's own data, with years and bed exactly as the listing states them; search links mark the beds we couldn't confirm, so check fit for your truck on those. The makers also name some beds differently: the F-150 short bed is 5 ft 6 in on the LOMAX listing and 5 ft 7 in on the MX4's.

• F-150: both have a confirmed listing for the 13th-generation (Gen13, 2015-2020) short bed. For the 14th generation (Gen14, 2021 on), the MX4 has a confirmed short-bed listing; the LOMAX short-bed listing is titled 2015-2020 though its part number is the one Agri-Cover lists for 2021 on as well, so a Gen14 short-bed owner should confirm with the seller. The LOMAX also has a 6 ft 6 in listing whose fitment line reads 2004 on, covering both generations, and we didn't confirm an MX4 for that bed. Only the MX4 has a confirmed Gen13 8 ft 2 in listing.
• Ram 1500 (DT): the MX4. Its 5 ft 7 in listing is for trucks without the multifunction (split) tailgate and its 6 ft 4 in listing for trucks with it; RealTruck sells both tailgate versions in each bed, plus separate RamBox parts, so match the exact listing. We couldn't confirm a LOMAX listing. Agri-Cover lists the 5 ft 7 in bed with and without RamBox, a separate RamBox version for the split tailgate, and the 6 ft 4 in bed without RamBox, and the one Amazon RamBox listing with LOMAX in its title carries a LOMAX Stance part number, a different cover.
• Silverado and Sierra 1500 (T1XX): the MX4, with 5 ft 10 in and 6 ft 7 in listings that work with the MultiPro and Flex tailgates; the short-bed listing won't fit the CarbonPro bed. We couldn't confirm a LOMAX listing. Agri-Cover lists 5 ft 8 in and 6 ft 6 in covers with and without the Multi-Pro tailgate through its selector and dealers.
• Tacoma: each has a confirmed listing for both generations, but for different beds. The LOMAX listings are for the 6 ft bed, on the 3rd gen for trucks with the deck rails and without the factory hard cover. The MX4 listings are for the 3rd gen 5 ft 1 in bed, built around the factory track system, and the 4th gen 5 ft bed. The LOMAX's 5 ft beds are search links.
• Tundra (3rd gen): both have a confirmed long-bed listing, the LOMAX 6 ft 6 in (2022-2025) and the MX4 6 ft 7 in (2022-2026). The LOMAX listing doesn't say which deck-rail version it is and its part number isn't in Agri-Cover's selector, so ask the seller. Only the LOMAX has a confirmed 5 ft 6 in listing, and its part number is Agri-Cover's deck-rail version.
• Maverick and Colorado/Canyon: both are confirmed. The MX4's Maverick listing reads 2021-2026, though the truck launched for 2022; the LOMAX listings read 2022-2026 for the Maverick and 2023-2026 for the Colorado and Canyon.
• Ranger (6th gen): the LOMAX has a confirmed 2024-2025 5 ft listing, and Agri-Cover sells a separate cover for 2026-2027. An MX4 listing exists, but its product page didn't show the fit clearly enough for us to confirm it.

Match the cover to the load

• Long or tall loads every week: the MX4, which opens the whole bed with the cover on.
• Tall loads now and then: the LOMAX. Lift it off in about a minute and leave the rails on the truck.
• Gear that has to stay dry: the LOMAX, plus a tailgate seal and the sealant in the box. If nothing in the bed can get damp, plan on extra seal with either one.
• A Ram 1500 or a Silverado or Sierra 1500: the MX4, the one with a confirmed listing for your truck.
• A 3rd gen Tacoma with gear on the deck rails: the LOMAX, which leaves the rails at their height. Read Agri-Cover's warning about some deck rail systems first.
• A rack: the MX4 TS on its T-slot rails, or the LOMAX with a stake-pocket rack such as Agri-Cover's ADARAC.
• Snow country, parked outside: the LOMAX, whose panels have no foam core to take on water. If you want the MX4 there, look at the EZ-Lift version.
• Coverage past year three: the MX4's 5 years, as long as you're the original buyer.

Drier bed or whole bed: our verdict

We'd buy the LOMAX. It keeps the bed drier, cost a little less on every bed where we could compare the two, needs no drain tubes, and comes off whole when the front third of the bed matters. Set the rails level, seal the bed cap corners, and expect a few drops at the tailgate.

Choose the MX4 if the full bed with the cover on matters every week, if your truck is a Ram 1500 or a GM half-ton, or if you want BAK's 5 years of coverage. Check it over the day it arrives, route the drain tubes out of the bed, and plan an afternoon of seal work.