They are spring-loaded. I also think most spring-loaded are actually made of delrin. I'm not 100% on that. The sticky here doesn't really say what kind of detents they are. But they are not rubber & will not wear out. Honestly I don't trust rubber detents anymore.
Some Invaluable Words of Wisdom:
A wise man's heart directs him toward the right, but the foolish man's heart directs him toward the left.
“If you're not a liberal at twenty you have no heart; if you're not a conservative at forty you have no brain.”
-Sir Winston Churchill
"Lousy Democrats."-Homer J. Simpson