- Sticks to smooth, nonporous surfaces like glass, plastic, fiberglass and tile. Extra strong with thick ribbed construction. Please be mindful that suction cups are based on suction and are not permanent - temperature and moisture changes can cause your suction cup to lose suction. We recommend testing your suction cup on a window for at least 24 hours using a towel or a non-breakable item to ensure solid suction. Test occassionally. Do not lick or add moisture, apply to a clean dry surface.