BAKFlip MX4 Hard Folding Tonneau Cover
The BAKFlip MX4 is our aluminum hard folding tonneau cover built for truck owners who need bed protection without sacrificing access. Its four-panel design folds completely open in seconds, giving you full bed length when you're hauling furniture, lumber, or anything taller than the rails. The matte finish resists scratches and UV damage better than gloss coatings, so it keeps looking sharp through years of sun and road grime.
We built the MX4 with FRP (fiber-reinforced polymer) panels backed by a heavy-duty aluminum frame. That combo keeps weight low—around 70 pounds for most truck beds—while supporting up to 300 pounds of evenly distributed cargo on top when closed. The dual-action tailgate seal keeps water out even in heavy rain, and the automatic latch system locks each panel without you fumbling with separate clamps.
- Four-panel folding design for full or partial bed access
- Matte aluminum finish resists UV fading and scratches
- FRP panels with aluminum substructure—300 lb. load capacity
- Dual-action tailgate seal blocks water and dust
- Automatic slam latch secures all panels with one motion
Panel Construction & Finish
Each MX4 panel starts with a fiber-reinforced polymer core that we bond to an extruded aluminum frame. The FRP layer gives the panel rigidity without the weight penalty of solid metal, while the frame’s box-section rails absorb impact if you accidentally drop a toolbox or tie-down anchor on a closed panel. We finish every panel with a powder-coated matte texture that hides fingerprints and minor scuffs—gloss black might look showroom-ready on day one, but it telegraphs every swirl mark by month three.
The hinges between panels use stainless steel pins and nylon bushings, so they pivot smoothly even when the cover is coated in road salt or mud. We coat the hardware in a corrosion-resistant finish, and the aluminum extrusions themselves are anodized before powder coating for an extra barrier against rust. That double-layer protection matters if you park outside year-round or drive in coastal humidity.
Folding Positions & Bed Access
You can fold the MX4 in three main configurations. For everyday errands, leave all four panels closed and locked—you get a low-profile bed that sheds wind and keeps groceries or gear dry. When you need to haul something taller than the bed rails, fold panel one against the cab; now you have three-quarters of the bed covered and about 24 inches of open height near the tailgate. For maximum cargo room, fold all four panels forward and they stack against the cab in a bundle about 12 inches thick, leaving the entire bed open.
The fold takes about 15 seconds once you release the latches. Each panel lifts on gas struts, so you’re not wrestling dead weight, and the struts hold each panel at a 90-degree angle while you’re loading. If you want to remove the cover entirely, pull two release straps near the cab and the whole assembly slides out of the rails as one unit. Two people can lift it off in under a minute, and reinstalling is just as quick.
Installation & Bed Rail Fit
Clamp-On Mount System
The MX4 installs without drilling. We ship the cover with a set of rail clamps pre-attached to the side rails; you position the cover on your bed, slide it forward until it’s flush with the cab, then tighten each clamp with a 7/16-inch socket or wrench. The clamps bite into the inside edge of your bed rails, so the cover stays put even when you’re driving over rough terrain or if someone tries to pry it open.
Drain Tube Routing
Because the MX4 sits inside the bed rails, any rain that lands on the cover runs off the sides and drains through integrated channels. We include two rubber drain tubes that you route down through the stake pocket holes near the cab—these tubes carry water out through the bottom of the bed instead of pooling against the bulkhead. If your truck has a bed liner, you may need to trim the liner’s rail caps slightly so the clamps sit flat; we include a template and instructions for that in the box.
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Common Questions About the MX4
The MX4 and G2 share the same four-panel folding frame and clamp-on install system, so their day-to-day operation is nearly identical. The main difference is finish: the MX4 has a matte powder coat that hides scratches and swirl marks better over time, while the G2 uses a gloss finish that looks sharper when new but shows wear faster. Both covers support 300 pounds on top and use the same latch and hinge hardware. If you park outside year-round or prefer a low-maintenance look, the MX4's matte texture is the better pick. If you garage your truck and want that glossy showroom appearance, the G2 delivers it.
Yes, the MX4 works with drop-in liners and most spray-in bedliners without modification. If you have a rail-cap-style liner like a Dee Zee or Rough Country that adds thickness to the top of the bed rails, you may need to trim the liner caps slightly so the MX4's clamp brackets sit flush. We include a trim template and instructions for that scenario. Spray-in liners like Line-X or Rhino typically don't interfere because they coat the bed floor and sides without building up on the rail tops. The drain tubes route through the stake pocket holes, so make sure your liner leaves those accessible.
When you fold all four panels forward against the cab, the stack is about 12 inches thick from the bed floor. If you have a cab-mounted toolbox, fifth-wheel hitch, or gooseneck ball behind the cab, measure your clearance first. The MX4 needs at least 13 inches of open space from the bulkhead to avoid interference. Most standard pickups have 16 to 20 inches of clearance, so you're fine. If you run a toolbox, consider a low-profile model like our BAKBox 2 that sits under the folded panels.
The MX4 is mostly maintenance-free, but a few quick checks keep it working smoothly. Every few months, spray the hinge pins and latch pivot points with a dry silicone lubricant—avoid oil-based sprays because they attract dust and grime. Wash the panels with car soap and water; the matte finish doesn't need wax, but a coat of spray-on UV protectant once a year helps prevent fading. Check the drain tubes after heavy rain to make sure they're not clogged with leaves or debris. If you drive in winter salt, rinse the underside of the cover and the clamp hardware every few weeks to prevent corrosion buildup.
The MX4's automatic slam latches lock each panel closed, and you can padlock the rotary latch handle near the cab to prevent anyone from opening the cover without a key. The latch handle has a built-in eyelet for a standard shackle padlock. That said, no tonneau cover is theft-proof—someone with a pry bar can force the panels or cut the clamps. The MX4's aluminum construction and tight fit make it harder to pry open than a soft roll-up, and the locked handle stops casual opportunistic theft. For high-value cargo, combine the cover with a locking tailgate or a truck bed vault.
The MX4 is compatible with factory and aftermarket tailgate steps like the Ford F-150's built-in step or the GM MultiPro tailgate. The cover's rear panel sits inside the bed rails and doesn't interfere with the tailgate's hinge or step mechanism. Spray-in liners are fine as long as they don't add thickness to the top of the bed rails where the clamps mount. Measure your rail width at the top edge—it should be between 1.5 and 2 inches wide for the clamps to grip properly. If your liner includes rail caps, you may need to trim them as noted in the install guide.
The MX4's flush-mount design and automatic latches keep the panels secure even at 75+ mph. The latches pull each panel tight against the weatherstripping, so there's no panel flutter or wind noise like you sometimes get with loose-fitting soft covers. Owners report better fuel economy compared to driving with an open bed because the cover smooths airflow over the cab and reduces drag. In crosswinds, the low profile and rigid panels don't catch wind the way a tall camper shell does. If you haul cargo on top, strap it down securely—high speeds amplify any load shift.