Rubber grommet bushings, mounting hole diameter: 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm 7 types, 260 pieces set, with case, for wiring work, protection, hole filling I opened it, but I haven't used it. Instant purchase OK. In addition to protecting wiring and preventing wire breakage, it also has excellent dustproof effects. If wiring is required, make a cut in the membrane and use it. No need to replace the grommets. Comes with a convenient storage case. If you have any other questions, feel free to comment.