This kit is of the screw in type and requires you to remove the ratchet and slidey brake assembly then open out the ratchet switch hole to 8mm to accommodate the knobby mag. The knob and spacer are manufactured from machined black acetal (engineering plastic) which matches the reel side plate and will not corrode; the remainder of the components are of brass or stainless steel so this kit is also ideal for angling use.