This economical Montolit Diamond Core Bit is made in Italy and will quickly dry drill many holes (25 - 35 each) in the hardest porcelain, ceramic and natural stone (granite, marble, slate and limestone) tile. Bit is designed to mount to a standard angle grinder 5/8" /11 standard thread without the use of an adapter (recommended 11,000 RPM). Average drill time of 20 seconds!