Handmade glass Harpley Slides are tempered at 1,060 degrees in a kiln for more than 6 hours. This creates a one of a kind look, feel, and sound in a glass that is tough as nails. Approx. 2.5" in length, these slides come in either 28 mm (approx. 3/4 inch) inside diameter Thick glass walls are just over 1/8 inch in thickness.