Acrow BT50 SM22 300 – Shell Mill Holder (Ø22 mm Bore, BT50 Taper) Acrow BT40 ER32 Collet Chuck Holder – 70 mm the Mini Mill Thread HARDCUT – Insize Surface Roughness Specimen Set ISR CS2 the Mini Mill Thread HARDCUT – 40 UN delivers unmatched durability Every unit is crafted from superior high quality steel and undergoes a rigorous ISO9001 quality inspection to ensure superior performance and reliability The Acrow BT50 SM22 300 is an extra long projection Shell Mill Holder designed for deep reach milling operations using face mills Constructed from hardened alloy steel and precision ground for superior concentricity