Set of 4, using a tube cutter. I suspect it's slightly off-spec from the 12mm size. Generally, 13mm outer diameter isn't a standard size, so this is based on what I have on hand. These are silicone tubes for replacing the feed and eject rollers of a ScanSnap ix500. Silicone tube: Inner diameter 6.5mm, Outer diameter 13mm, Length 24mm (approximate) These are for replacing the deteriorated roller rubber of a ScanSnap. There are two methods: complete disassembly or partial replacement by making a vertical cut. This can be used as is for complete disassembly, or by making a cut for partial replacement. Method for complete disassembly replacement: It's too involved to write out here, so please search online. There's no difference in normal use, and although it takes time, the appearance will be perfect. Method for partial replacement: 1. Remove the feed and eject rollers by making a vertical cut with a cutter and pulling them off. If hydrolysis has progressed, you'll need to use anhydrous ethanol and cotton swabs to remove the stickiness. 2. Make a vertical cut in the new tube and set it on the shaft of the feed and eject rollers, using the rotation of the power button. I haven't done it, but you may need to use adhesive. If it slips, use adhesive to secure it completely. This is just the surplus I bought personally, so the quality is different from what companies sell. If you are concerned about burrs, please purchase from them. If the quantity is insufficient, a refund will be processed.