The Santoprene inserts are available in grey , black and yellow.
What is Santoprene?
Santoprene™ TPV is manufactured by ExxonMobil.
Some of the physical characteristics is that the rubber is very robust and flexible and is flexible.
Unlike some PVC inserts . Polyvinyl chloride is the world's third-most widely produced synthetic plastic polymer. Most people use it in hard plastic situations such as piping. In its natural form it is hard, brittle and white. In order to make it flexible plasticizers are added. The problems with plasticizers , is that after a time they can shrink especially when exposed to weather situations.