I lost several 'biners to deep rope grooves and started looking at buying rescue/professional hardware since it's all made of steel. I almost did it, but couldn't stomach the size/weight. Luckily edelrid makes a line of carabiners called "Bulletproof." Lightweight aluminum biners with a small steel plate on the rope-bearing surface. I've descended a couple thousand feet at this point using it and there is no rope groove At All. I've also noticed it stays significantly cooler even when rappelling quickly. This makes sense because steel has a MUCH lower thermal conductivity coefficient. So the heat generated by the rope doesn't spread to the rest of the device and instead stays right on the little steel plate. I have the screwgate belay carabiner in the bulletproof line and I checked and it is compatible for sure with a Critr and Pirana. I think everyone should use these things, especially on canyons where your rope gets real sandy. P.S. I swear I don't work for edelrid, these things have just eliminated my need to buy more carabiners indefinitely and I wanna spread the good news. They make 'em in every style and function to suite your fancy.