The Grip-Tite® locking System on all Crain prism poles, eliminates elevation errors due to malfunctioning locks. High-strength elastomeric pads grip the telescopic sections and can be adjusted with an allen wrench (included). Crain prism poles come with a Topo-Boot® and have a standard prism offset of 0.500 ft. (152.5 mm.). The grads are in in 0.01 ft. and cm. The adjustable 5/8 x 11 adapter may be preset with a 0.27-ft. (82.55 mm) range to accommodate a broad range of prism heights.