Double Convex Glass Lens, 50mm Diameter, 300-1000mm Focal Length Range Grade_Food Grade with values marked on the

with values marked on the panel for direct identification during student bridge work

Tensioner pulley keeps chain engagement consistent on this hand-cranked chain drive

Blue 300mm 2mm-stackable lead with nickel-plated split-hollow pins

wheel-and-axle

5 newtons for measuring small forces during spring-law and tension-force classroom investigations

Double Convex Glass Lens, 50mm Diameter, 300-1000mm Focal Length Range Grade_Food Grade with values marked on theBuilt for long bench convergence flexibility, a 50mm double convex glass lens spanning 300 1000mm focal lengths gives projection style optics setups a single range rated element.