The tapered barrel of the bobbin allows for half-hitch and whip finish knots to slide smoothly onto the hook. A new O-ring grip acts as thread keeper when finished tying. And of course, they come standard with the Rite Adjustable Thread Tension System, each click on the brass star tensioning knob gives you 1-oz of pressure (adjusts from 2-16 oz of thread tension!). Finest quality surgical stainless-steel.