The A55M Shock Stopper from Shure is a high-quality isolation mount and swivel adapter. The mount has standard threads for use with a variety of mic stands and boom arms. The full-circle design provides a secure hold, and the built-in elastics provide isolation from unwanted vibrations. The mount is compatible with virtually any tapered microphone, including the SM57, SM58, SM86, Beta 57A, Beta 58A, Beta 87C, and KSM109.
Shure makes the A53M for smaller diameter body mics like the Shure SM81 (which fit a lot of smaller diameter mic bodies like my Gefell M300 mics) and these slightly larger A55M shock mounts which will hold a mic body like the Shure SM57. So we are looking at two different diameter accommodating shock mounts. These are low profile shockmounts that take up not much more space than a typical plastic mic clip. Therefore these low profile shock mounts are perfect for fitting into tight places, like on toms or a snare for a drum set, or on a short stand in front of an amplifier. And since these shock mounts are small, they are also no extra eyesore for on stage, like a Rycote might be---so the A55M will work great to isolate a mic on a stand in front of a performer, avoiding low end thumps or noise transferred through the mic stand (think here---someone bumps the stand, or jumps on the stage--that energy is not transferred through the shock mount = NICE). Do these deliver results of a more robust shock mount? No. That is not the intended use. Do they solve shock problems on stage ? Yes, for the level a live stage requires, anyway. This shock mount and its smaller sibling that A53M are awesome tools to have onhand to give live sound and live recording engineer a way to keep rumble, bumps, and avoid transferring stage floor noise through their microphones.
The device works well enough. Most surface disruptions and walking around are not picked up through vibration. I am curious to know how long it will last and keep its shape. The rubber it is made from appears it will start to give in a couple years. For the price it's a fair piece of equipment which I would recommend to someone looking to isolate an sm X microphone.