2 pair of roller style guitar string retainersThe rollers on them can lessen the stress on your strings, which allows the guitar to stay in tune longerThey also can prevent wear and tear on the strings, which results in longer string lifeCompatible with electric guitar and bassThis is a set of 4 chrome roller string trees.These string retainers are the type with the little rollers on them to help stay in tune and help prevent strings from breaking.They come with 4 mounting screws as well.Great replacement compatible with your broken, dirty or old string retainer.Sure to look great on your guitar Base Size (L x W): Approx. 0.43 x 0.23 inch / 11 x 6mmTotal Height: Approx. 0.47 inch / 12mm (including the roller)Roller Size (L x D): Approx. 0.4 x 0.2 inch / 10 x 5mmString Spread (Center to Center): Approx. 0.27 inch / 7mmMaterial: Zinc alloyColor: ChromePackage Included:2 pair of guitar string retainers4 x Mounting screwsOnly the above package content, other products are not included.Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.