I bought a pair of these beater heads to replace the worn-out original beater heads that came with my Iron Cobras. (I had played almost 100 gigs with them, as well as hundreds of hours of rehearsals, so I have nothing bad to say about their longevity!)
Fitting them is very straightforward, requiring only a drum key. Loosen the single bolt, turn the head through 180 degrees (so the felt side faces the back) and lift off. Pop the new one on (also upside down and backwards), rotate until it faces the front, and tighten the bolt. It takes seconds.
Note that this package does not include the shafts - this item is the beater *head* only. So it's only suitable as a replacement if you already have Iron Cobra beaters with the cylindrical T-bar at the top. If you're replacing a different model of beater, then the item you need is the CB90F, which includes the shaft.
