Whiteside Screw Type Helix Mortise Cutter Arbor 1/4 in. SH x 5/16-24 TH is designed for use with Whiteside's Helix Mortise Cutters, which are sold separately. This versatile arbor can be used in both hand-held and machine routers, making it a practical choice for various woodworking applications. It features a 1/4-inch shank size and a 5/16-24 end thread size, ensuring compatibility and secure attachment. Manufactured by Whiteside Machine Company in Claremont, North Carolina, this arbor reliable performance and durability. The overall length measures 1-3/4 inches, providing a compact yet efficient tool for precise mortising tasks. Model Number: HMA-1/4A