To make the Racing Ralph the ideal cross country tire, Schwalbe uses the PaceStar compound for the tread. By using a center strip with a medium durometer and shoulders that have a softer durometer, the Ralph is able to roll fast on straights while gripping turns so you won't have to sit on your brakes. It's basically free speed. And, so that a flat won't end your day, Schwalbe's Ralph comes in two different levels of puncture resistance. If your ride or race covers rocky sharp granite and cacti, the SnakeSkin is the optimal choice. This option makes tubeless conversion simple with no need for sealant. If your trail is slightly less sharp, the LiteSkin is ideal this option also takes 70 grams off the weight of each tire.