These flat washers are made of high quality silicone which is high temperature resistance, non-toxic and no smell. 

all purpose anti dust T type silicone rubber hole plug stopper end cap chock for cartridge push in stem bumper
★ Food Grade Silicone ★ Our airlock stopper is made from the food grade silicone.It features a healthier/ environmental/anti-corrosion/heat resistant/waterproof/high wear resistance

★ Provide A Tight Seal ★ With the use of silicone plugs on airlock for the beer fermentation can be carried out a good isolation of the air ; for honey, white wine, milk alcohol fermentation can Prevent oxidation

★ Great For Kinds Of Airlocks ★ This airlock plug is perfect for the common fermentation airlocks and the counter pressure bottle filler. Silicone stoppers have a various diameter sizes to fit any vesse

★ Great For Kinds Of Carboy ★ This silicone stopper is fitted for carboy & bubble airlock & glass fermenter. We have marked the dimensions of each model on photo