Set of 4, using a tube cutter. I suspect these are outside the tolerance for 12mm items. Generally, 13mm outer diameter items don't exist, so this is limited to what I have on hand. These are not genuine products. These are silicone tubes for replacing the feed and eject rollers of the ScanSnap ix500. Silicone tube: Inner diameter 6.5mm, outer diameter 13mm, length 24mm (front and back are the same). These are for replacing the deteriorated roller rubber of the ScanSnap. There are two methods: complete disassembly or partial replacement by making a vertical cut. These can be used as is during complete disassembly, or by making a cut for partial replacement. Method for complete disassembly replacement: There are too many steps to write out, so please search online. There is 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 will need to remove the stickiness with anhydrous ethanol and cotton swabs. 2. Make a vertical cut in the new tube and set it on the shaft of the feed and eject rollers while using the rotation of the power button. I haven't attached any, but you may need to use adhesive. If it slips, use adhesive to completely attach it. This is at the level of selling the leftovers I bought personally, so the quality is different from what companies sell. If you are concerned about burrs, please purchase those. If the quantity is insufficient, a refund will be processed.