The ST-HS Plumbers bi-metal hole saw set contains six of the most commonly used hole saws for the plumbing trade. Whether you are using the 19mm for loft tank connectors, the 29mm for installing bath taps, or the 57mm for boss adaptors, these 4/6TPI variable pitch, M3 HSS Bi-metal hole saws provide fast, reliable cutting, and proficient swarf removal through thin and thick gauge materials.