they are BPS. And going up them isn't as bad as coming down. I will never forget one year when I was a lot younger I got one of those vinyl covered "thermo seats" - you know the ones filled with tiny styrofoam balls to keep your butt warm when sitting?
I was coming down one of the mtns. after 3" of fresh snow fell. About 1/3 the way down I slipped and landed on this cushion that was attached to my belt. The farther I slid on that thing the faster I went. After about 50 yards and going about mach 3, the cushion detatched from my belt but my momentum carried me another 25 yards. Looking back up the mtn I saw the tattered cushion and styrofoam balls rolling past me. I was fortunate not to have collided with a tree and all that I hurt was my pride.