Planet Waves Glass Slides are made from boron silicate for enhanced durability, smoothness and tone. The medium slide is perfect for players who like a knuckle length slide for their 1st, 2nd or 3rd finger. Each Planet Waves Glass Slide is individually heat treated to provide smooth edges and a perfect finish allowing the slide to glide over strings while the 4mm glass thickness produces a warm, thick tone. These slides are available in small, medium and large sizes.