This button is designed for use with thumb-trigger release aids. The hexagonal helix allows your thumb to find a consistent placement as you execute your shot. Measures 20mm (h) x 18mm (w). Includes a hole which will allow the standard M3 bolt (which comes with your release aid) to screw in. The hole is unthreaded, but the M3 bolt will tap its own thread. This is an original design based on a common concept.