The sidewinder is an interesting thing. It’s a magazine feed conversion kit available for the Mossberg 500 and 590; along with a system of six round box, or 10 round drum magazines. This allows for rapid reload, and rapid changes of ammunition type, which I appreciate; as well as greater magazine capacity in the shortest possible barrel length (no long mag tube extensions).
I should say it WAS available; last month Knoxx took it off the market, because they couldnt manufacture it economically for the quality they wanted; and belive me that quality is very high. Although the finish on the kit leaves much to be desired, it is INCREDIBLY tough. There are videos on the Knoxx site of the sidewinder mags being run over by pickup trucks, and thrown 30 feet onto the ground with no more damage than scratches.
Hat Tip: GunPorn