I've had this for a few months now, and I've even pitted it against the Rocket Cock 2 from whoever makes that. There is NO comparison. BT's Sealed bolt system is without a doubt one of the best 'mods' available for the 98c.
The Sealed Cocking System does in fact quiet down the operation of the marker, as well as prevents dirt, grime, and other debris from getting into the inner workings of the 98c.
Installation is also a breeze. It's as easy as replacing the cocking rod and bolting the Composite pieces on using the supplied hardware.
I love this thing. It's made my 98c quieter and it just looks really cool!