The conveyor floor slat is an extruded translucent UHMW polyethylene member with a top plate and two side walls. The top plate has an upwardly facing cargo support surface and a downwardly facing bearing surface between the two side walls. A support and hold down flange with a downwardly facing horizontal support surface and an upwardly facing horizontal hold down surface is integral with the bottom edge of each side wall. The UHMW polyethylene can be formed by extrusion, reduces slat weight and requires less force to reciprocate back and forth to discharge cargo than expected. A rubber like seal can be mounted in a seal holder on the outboard side of one sidewall. A seal contact flange is integral with the outboard side of the other side wall.