Primary Arms SLx Reflex Offset Keeper Mount Black. O.K. (Reflex Offset Keeper) is an upgrade accessory for our SLx Scope Mounts allowing you to attach a reflex sight to the mounts keeper. Also compatible with our zero-cant PLx Mounts. Specifications for Primary Arms SLx Reflex Offset Keeper Mount: Manufacturer: Primary Arms Color: Black Features of Primary Arms SLx Reflex Offset Keeper Mount Fits: SLx and PLx Cantilever Mounts Package Contents: Primary Arms SLx Reflex Offset Keeper Mount Primary Arms 910099: SLx Reflex Offset Keeper Mount Black