#8 stopper - with 3/8 inch hole. Top diameter 1.59 inches (40.5 mm), bottom diameter 1.31 inches (33 mm), length 1 inch (25 mm).

With so many places you can use this stopper, it pays to keep a few extra around. This #8 Silicone Stopper With Hole fits some 1 gallon glass jugs. It can be used with an airlock or without, by simply using a #000 solid stopper to plug/unplug the hole. Easy to clean and sanitize. Size 1 5/16" - 1 10/16".