The well assorted and extensive 170 spiral drill bit assortment from 1 to 10 mm is made of high quality hss high speed steel and is coated in titanium all drill bits are easy to find in the sturdy system metal case where they are safe but close at hand the extreme hardness of the titanium nitride layer gives the titanium drill bit its unsurpassed wear resistance the titanium drill bit has up to 6 times longer life than normal hss drill bits contents 10 x 1 mm 10 x 15 mm 10