D'Addario's Glass Bottle guitar slide is based on the specifications of a vintage medicine bottle. The design is the secret behind the tones of many slide players past and present. With a unique glass surface and light weight it offers excellent tone, sustain, and playability. Perfect for acoustic and electric guitars. The opening measures 13/16 inch, (.81" / 20.6mm I.D.), 2.58 inches long (66mm length). You need different slides for different sounds to match the mood of your music. This would be a great addition to your arsenal of slide sounds.