I have size 11 rock boots and use XXL jets. No problem, but I also use small (as in shorter) spring straps for a tighter fit with that huge pocket. XL jets WILL BE TOO SMALL with your 12 rock boots. Trust me on this. I couldn't use the XL jets with my 11 rock boots and it wasn't even close. I tried it. For some reason the size jump from XL jets to XXL is crazy! Mad crazy yo, as the kids say here on the subway, lol. The XXL really should be the XXXL version, lol.
The Turtles are perfect with my 11 rock boots and regular size spring straps. My wife owns the turtles and sometimes I use those too. I suggest the turtles as that XXL Jet is huge and I mean the entire fin itself as well as the foot pocket. I don't mind it with the shorter spring straps, but you might if you like fins to fit tightly or if you hate large paddle fins. Personal choice. Good luck!