Steel spring with looped-ends 19mm diameter, 56mm length from the ends of the loops Stretches to approximately 290mm without deformity Ideal for depicting Hookes Law and other physics concepts 1 Spring This 19mm spring is made of durable steel and designed for classroom applications involving Hookes law and other physics concepts. It is 56mm in length, 19mm in diameter, and stretches to approximately 290mm without deformity.