its called a tube adaptor, it clamps to your vise and lets u tie tube flies. Cost about $35- 50, benefits is u can use normal octopus hooks on big flies, so the leverage factor of the old school low water hooks isn't against you, and u dont have to tie a turle knot, u can just tie it on normally or with a loop knot. It lets u stack flies, u can change flies way faster, and u dont need a fly box, just some ziploc bags with the different types of tubes u tied up. U tie the flies the same way u do on normal hooks, the tubes can be made out of metal or plast or rubber, depending on the weight and action u want.
the adaptor i have is the spratley model and i personally love it, because it has a tension collar, once u lock down the wire with tube on it, u turn the tension collar and it completely secures the tube, doesn't spin when tying.