Thes stoppers are made from flexible, red synthetic rubber. They are designed to fit round openings that are 3/4" diameter and no more than 3/16" thick. The height of the plug from top to bottom is 1/2". For the best fit, measure your opening to the nearest 1/16 of an inch. A US company in business since 1949, National Artcraft is a name you can trust. This very flexible, red synthetic Stopper or Plug is designed to fit a 3/4" diameter round openings.   Please measure carefully. Also, see the secondary image for correct hole size measuring. These plugs are suitable for a variety of applications such as jars, vases, home appliances, panel plugs, crafts, hobby ceramics and other similar applications. The groove on the side will accommodate material that is no more than 3/16" thick. The height of the plug from top to bottom is 1/2".