Moulded Glass Rock Slides are individually hand moulded by master lampworkers. These have all the same features as the brass Rock Slide with the knuckle cut, finger rest and tapered interior, and fit almost exactly like their brass counterparts but are slightly longer. The main difference is that they are much lighter and faster, so you can really cook with these on an electric guitar - and because of their unique tapered interior design, they also have enough mass to light up your acoustic.