What are the types of rubber?
There are two basic types of rubber used today in cars and trucks.
Dense rubber is harder and used for gas and brake pads, hood bumpers etc.
Cellular Sponge Rubber
Cellular sponge rubber is used for weatherstripping , to seal doors, trunks, hoods and roofs. Sponge rubber varies in degree of softness from one manufacturer to the other. The greater the softness, the better. Softer rubber does a better job filling in the tiny cracks and bumps along surfaces it presses against. This prevents water leakage. Softer weatherstripping also makes it easier to close doors, trunks and tailgates.
METRO's SUPERSoft sponge rubber is the softest and most durable auto rubber you can buy. SUPERsoft has a unique closed micro-cell structure. This cell structure helps give SUPERsoft its superior softness. The material formula and secret manufacturing process gives SUPERsoft better shape "memory", better looks, and better durability and resistance to abrasion, tearing and ripping. Unlike other auto weatherstripping, SUPERsoft does not absorb water – a key condition to completely sealing out water.