Unthreaded stylus holder with M5 threaded base. Holds up to 5 unthreaded styli with 1.5 mm diameter stems. Features a 1.5 mm diameter knock-out hole through threaded base. Stainless steel, with stainless steel set screws. Weight is 7.38 grams. Includes hex wrench (pictured). Compare to Renishaw A-5555-0106 and Zeiss 600341-8368-000.