Love my ZZ. I use it singly for DdRT and also in tandem with a RW for SRT. Very smooth on descent, easy to use, BUT not midline attachable. Also have a Bulldog Bone which IS midline attachable and very handy but not quite as smooth on descent on any of my ropes. Often use them both on a climb where I might go up initially on the ZZ/RW but have the Bone racked on the saddle if I want to use the tail of the climbing line or the other end of a long lanyard for moving around or shifting the TIP up. The ZZ has an additional advantage if one wants to add some MA with a pulley hung above it on an ascender, since the ZZ has a pulley on the tail side which fairleads the tail back up nicely. This doesn't work as well with the Bone. Also, a Captain Hook is money well spent. I have one on the other end of my long lanyard and it is a great asset, very easy to get the hang of tossing and retrieving it, and it has multiple uses. One other thing (which I learned about here on the Buzz, thanks guys!) that I never climb without now, is one of those old time spring-loaded fly fishing reels. They are cheap on eBay and easily hold 50 to 75 feet of throwline. They are a great time saver for managing a throwline up in the tree.