As most people take their hand off the handle on every stroke for the 550, a roller handle doesn’t make as much sense as say the 650 or 1050. I actually found it to be slightly inconvenient on the 550 and highly prefer the ball handle. (My preferences, yours may vary.) The strong mount is give-or-take. @jmorris is spot on with his comments about them being two pieces of sheet metal. I bought my 550s second hand, and they came with them, so I’ve continued to use them. Otherwise, I definitely wouldn’t pay the $60 they are asking for them. Bolt directly to the bench, or to a plate on T-track. I suppose one alternative reason is using a bench that wasn’t built at the necessary height and wanting to get the press higher for visual purposes.