One-piece expanding jam chuck set. Chuck sizes: 3/4", 1", 1-1/4", 1-1/2", 2". 1-1/4" long with 1/4" shank. Works perfect with cjam10f 5-Piece Forstner bit set to drill out the jam chuck holes. Ideal solution for securing turning projects such as goblets, bud vases, and other items with hollow centers. Insert the tough rubber chuck into your work, then expand it by turning a nut to secure the work piece.