Mopha via Amazon offers its Mopha 15-Piece Diamond Drill Bit Set for $17.99. Coupon code "MVBVF3AH" knocks that to $12.95. Plus, Prime members bag free shipping. That's $5 off and the lowest price we could find. These nickel-plated carbon steel bits feature diamond dust-coated heads, which cut through tile, glass, porcelain, marble, and more. The set includes 15 sizes of bits, ranging from 4mm to 50mm. Deal ends June 30.