RGS - Bridge Riser Block SetEasily add thickness capacity to any RGS unit by adding these Bridge Riser Blocks between the bridge extrusions and long axis linear slides! Each set contains four blocks with associated hardware and will raise the bridge extrusions by 3 4 inch. One Foundation Set is required for the first 3 4 inch lift and are engraved with an "F". Additional increases are handled with Riser Sets and each set will add a similar 3 4 inch to the capacity. Riser Sets