The Dunlop 213 Pyrex Glass Guitar Slide is constructed from durable, seamless heat-treated Pyrex boron silicate glass.  It features a heavy wall thickness and is size large.  It fits roughly a size 13-14 ring.  The inner diameter is  approx. 7/8" and the outer diameter is approx.  1 1/4".   This slide provides excellent tonal clarity and sustain for guitar players. Made from high-quality Pyrex glass, this slide offers a smooth and responsive feel on the guitar fretboard. The clear color adds a sleek and professional look to any performance.