Road Stud – Tempered Glass – 3 15/16″ x 3 15/16″ x 1 31/32″ – 30 Ton This road stud is made from high quality tempered glass, and is highly reflective on both sides. It has dimensions of 3 15/16″ x 3 15/16″ x 1 31/32″ and a compression resistance of 30 tons.