Suitable for glass, mirror, ceramic wall, tile, smooth metal , bathroom tiles wall, kitchen tiles wall, glass shower screen, glass window. Don't work on pitted/uneven surfaces. TIPS: Make sure the object is clean, smooth, no dirt and no oil stains. You can dip a little bit of water in the inside of the sucker before you stick the sucker, so as to stick more firmly. Package contains: 30pcs thread suction cup 4cm, with knurled nuts. Diameter of the cup is 40mm. Thread height is 6mm. This thread suction cup is made of high-strength transparent PVC plastic, soft, , waterproof, not easy to fall. Other Uses: Can be used to fix insulating covers to the inside of . Or use these suction cups to attach windbreak along the lower side of motorhome, within an awning. Use them in the car to hold sun shades up to shade the kids., Manufacturer: Jnchdghwa