Durable 6mm (1/4") phenolic material. Single pivot can be locked to make circles up to 1.32m (52") diameter. Creates wide range of circles and ellipses. Comes with jig arm, jig base, two dovetail keys and two locking pivots. Minimum circle diameter 235mm (9-1/4"). Can be used with vast majority of plunge routers. 9-1/4 - 52"