Straight Line Sumo Seatsac 125 Ballast Bag 2010: Incoming! Get ready for the Sumo Sac, the super flexible, puncture-resistant ballast bag newly available from Straight Line. If you’re having difficulty comprehending how tough they are, think elephant skin, but with a conveniently thin, sandwiched, woven polyester core and glued and taped seams to make this bag practically indestructible. When 2012 hits and the world is being sucked through a black hole, remember, your Straight Line Sumo Seatsac 125 Ballast Bag will probably still be holding on strong.