First-hand experiences with wheels, gears, pulleys and cams are an important part of design technology and STEM education. SI offers an assortment of these materials designed to work with either 3 mm BBQ skewers or 3/16" dowels. Gear sets offer 40-, 30- and 20-tooth gears with 3/16" bore to accommodate the most popular dowel size, and a 12-tooth gear with a push-fit to 2 mm motor shafts. Three inserts are provided on each sprue, allowing the 3/16" bore to reduce to 3 mm. Gears are beveled for 90° meshing. The 40-tooth gear has an additional hole to create an eccentric movement, or to use with a crank handle. Assorted colors.