This is a pack of five Avid RC 1/8 Scale Exhaust Gaskets. Avid gaskets come in a tube of 5 and are used to create a safe seal on .21/.28 engines where the exhaust port of the engine meets the header of the exhaust. Another gasket is typically used further down the line where the header then meets the exhaust pipe. It is very vital to have gaskets in good solid condition. A torn gasket can lead to tuning issues, possibly glitching on older radio systems, and the worst case scenario of dust getting sucked into the engine and scratching your sleeve and eating your bearings.
Avid gaskets are softer than the majority of gaskets on the market in order to great a solid seal between the two parts. If there is any leaking from a hard gasket you are introducing cold air into the flow of exhaust which will mean a loss in efficiency which could possibly lead to loss of power and fuel mileage. It is unlikely that anyone will be able to tell the difference but you can rest assured that there is no chance of this happening. Because of the softer material it is important to not overheat your engine 280f+ and if you do it will always be smart to check your gaskets.