I think the fish on my local have been wising up to biscuit flies of late ( I have hammered it ! ) , and noticed a marked difference using these:
There is a knack to presenting them, make a slice in the long side, and add cryo, then drop in your hookshank. If you don't glue them on, they will twist, and you will miss bites. They sit very low in the water, so a small piece of hi viz foam or biostrike on top will help your eyes. Pre soak chum mixers, as they sit lower, just like the hookbait..
And I would not have believed it, but these are what I currently use as they top the lot. Glued on the hook the same way, fished with dog bics. You wonder what they look like from under the water, and what colour spectrum the fish see in, but they are deadly on my water: