I would say BCY-x and X-99 are the 2 quietest I have used. Both quieter than D-97.Bisch
If for a Covert Hunter... I recommend a Mountain Muffler string over a specific material.They really quiet the big hooks. Feel free to send me a message for more info...FF+/D97 or m last one was 8125. The 8125 seems to be a bit stifferFF+ and D97 are same material but in different size strands, by different makers.Stay away from BCY-X or 452 unless you get approval from the limb/bow maker.My Borders are not warrantied for use by anything other than D97 or 8125. I know that other makers are the same.
I really like 452x. I liked 450+ but I like 452 x even more. I use 18 strands and single serve perfect for carbons and wood, might need a wrap of floss but you could cut 1/2 the string and still use it. Strong and quiet. Doesn’t move and very little fuzzing.