Rubber Grommet
3/8 inch - Seals 1/4 inch (6 mm) in 9/16 inch (14 mm) hole size
1/2 inch - Seals 1/2 inch (13 mm) in 7/8 inch (22 mm) hole size
3/4 inch - Seals 3/4 inch (19 mm) in 1 inch (25 mm) hole size
1 inch - Seals 1 inch (25 mm) in 1-3/8 inch (28 mm) hole size