PC20 Relton Porcelain Cutter 1-1/4" Finish Hole DiameterFor Installing: Reverse Osmosis Systems Hot-Water Dispensers Spa Jets in pre-existing bathtubsDrill through porcelain and cast iron with pilot bitDrill through porcelain only with spring-loaded sawDrill through cast iron with finish sawRelton Porcelain Cutter Kits are designed with the Finish Saw 1/8" smaller in diameter than the Porcelain Saw. The Finish Saw diameter is used to determine which kit should be purchased