Tying with synthetic quills is a breeze compared to most natural quills, and Perfect Quills from Semperfli make it even easier. The clear, transparent quills have a dark edge to give body segmentation, allowing you to simply wrap whatever color of thread, wire, or tinsel underneath that you desire, and then wrap the quill over the top to create the perfect segmented body, without having to buy a whole bunch of different color quills. These quills are tapered with adhesive on the back side, so the quill will stay in place as you wrap it. Coat with UV resin and you have a beautiful and indestructible segmented body.
In regard to the three sizes, all of the quills themselves are the same, with the size referring to the thickness of the dark edge, meaning the large size will have a very pronounced, dark edge while the edge on the small size will be more subtle. Semperfli recommends using size small on flies sized 16-22, medium on flies 12-16, and large on flies 8-12.