Dunlop 213 Heavy Glass Slide - Large Diameter - The Jim Dunlop Glass Guitar Slide, heavy wall thickness, UK ring size Z3, is made from tempered glass which gives full, rich tones that are warmer and more resonant that metal slides. Great for both electric and acoustic guitars, giving very pure tones Choose Dunlop Tempered Glass Slides for a warmer, thicker tone accentuating the middle harmonics of your sound. Today's most popular slide. Processed from high quality Boron Silicate. Heat treated and annealed to produce a flawless tube. • MFSKU 213 • UPC 710137000247