I have big problems with these kinds of loops. The tru-fire version weighs 80 grains. The types of metal D loop are bad, bad, bad. Put on a string D loop or have a pro shop do it for you.
I had a customer come in and say my fletching is hitting my rest and damaging it. I thought that was a strange comment. I took his bow and looked at the rest. It had a whisker biscuit on it. There were chunks of aluminum missing. Fletching will not do that. Then I noticed the metal D loop. It too had some marks on it. The D loop would go all the way up and hit the rest when he shot it. This bow had 7 INCH brace height. Had it been a 6.5" brace height bow, it probably would have ripped the rest of the bow when it was shot.
I cannot stress this enough. Do Not put these on if you want the best performance and most forgiving setup. I haven't even mentioned the speed loss. This is just my opinion.