The top of your camera can often be unused space, but it's ideal for accessory placement and adding (or replacing your camera's plastic grip with) a solid, secure, multi-purpose Top Grip. To complete your rig the Zacuto 5 In. Z-Rail is used with camera specific top mounts. The 5″ Z-Rail attaches via (2) 1/4" 20 screws (included) that are spaced 3/8″ screw center to center at their closest to 4 1/8″ at their furthest. This long Z-Rail is particularly helpful when using the Zacuto Axis EVF Mount with the Black Magic Camera so there is more clearance to adjust the EVF mount.