Catgut is a great fly tying material and flies tied with a catgut look very realistic.
Size L is for hooks #8 and #10Size M is for hooks #12 and #14Size S is for hooks #14 and #16Size XS is for hooks #16 and #20L=0.7mmM=0.5mmS=0.3mmXS=0.2mm
This material has already become a classic in tying, mainly for Caddis/Sedge larvae and shrimps . It is a water stable and very easy to work with. The fluorescent colours are ideal for shellbacks for shrimps.