The UnderCover Flex is a folding tonneau cover for the 6 ft 4 in bed of the Dodge Ram 3500, and it will not fit trucks with RamBox. Its FRP composite panels rest inside the bed rails, built-in prop rods let the truck be driven with the cover fully open, and rubber seals and drain tubes channel water out of the bed.
A tonneau cover closes over the open cargo box of a pickup truck to hide and shelter what is carried inside; depending on the design it rolls, folds, retracts or lifts open for access.
Listed for 2 vehicles: the fitment table on this page shows each year, make and model it fits.
Part number: FX31004
Manufacturer data for this part — all visible, no tabs to dig through.
| Brand | UnderCover |
| Part number | FX31004 |
| Shipping carton | 81 × 31.8 × 8 in (206 × 81 × 20 cm) |
| Shipping weight | 29.9 kg (66 lb) |
| Category | Truck Bed & Tonneau |
More parts for the 2019-2026 Ram 2500/3500. Untick anything you don’t need.
$1,749.99
$475.99
$709.99
More in UnderCover.
Free shipping
Free shipping
Free shipping
Free shipping
Free shipping
Free shippingAll Truck Bed Covers & Tonneau Covers for the Ram 1500 2009–2018 →All parts for the Ram 1500 →
All Truck Bed Covers & Tonneau Covers for the Ram 1500 Classic 2019–2024 →All parts for the Ram 1500 Classic →
From MapleTorque customers
Awesome Send an email get reply very promptly... Send an other email weekend time ... Also get reply immediately... Alex take care of the customer to make sure everything going good during the transaction... #1 2026 Keep continu...
Quick shipping and very smooth transaction and I will certainly be checking here for future needs
Excellent shopping experience with MapleTorque! Alex was incredibly responsive, friendly, and genuinely committed to customer satisfaction. He personally helped me with pricing, made the purchase process easy, and even followed up after ...
New arrivals, restocks and fitment tips — straight from the counter.
