Clear Glass Rock Slides® are individually hand moulded in the USA by master lampworkers. These have all the same features as the brass Rock Slides® with the Knuckle Cut, Finger Rest and Tapered Interior. These fit almost exactly like their brass counterpart but are slightly longer. The main difference being that they are much lighter & faster so you can really cook with these on an electric guitar. Because of the unique tapered interior design they do have enough mass to light up your acoustic. They ALL feature a 4mm thick wall. Inside diameter: 17.5mm Total Length: 48.5mm Weight: 31g