JessEm 02025 4-Piece Tab-Loc Insert Ring Set 4-piece Tab-Loc insert ring set Easily change the bit hole diameter in your JessEm router plate Precision machined from solid 1/4-inch thick phenolic; pre-drilled center holes of 1/4, 1/2, 1-3/8 and 2-1/2-inch diameters Designed to be used in JessEm Tool router table insert plates and router lifts 3.8 by 3.8 by 1 inches; weighs 8 ounces