These HSS bits are designed to meet the needs of pen makers. Precision ground bits start cleanly and limit exit hole chip out. Featuring deep smooth flutes for superior chip extraction and extra sharp lands and flutes which provide precision sized holes in your pen blanks with fewer lost blanks. Bits with shanks 31/64" and 11mm or larger have shanks reduced to 7/16". Pen Maker's Bit Set contains the bits required to make the most popular kits. Contains one each 7mm, 10mm, 11mm, 27/64", 3/8", and letter "O" bits.