It is a Openings Locator/Hole Saw Guide Jig Fixture. Minimum Drill Bit Dimension: 1/8", Maximum Hole Saw Dimension: 3-1/4", Material: Engineering Plastics & Ball Bearings, Long Lifespan & Durable Service. Application: Available for Ceramic, Glass, Granite, Porcelain Marble or any smooth surface where the suction cup base can hold on - Including Walls.