Sm57 = Sm58
Foreverain4 is correct, they're the same. I use an SM57 for amps/cabinets, then use it with a pop screen if I use it for vocals. Which, by the way, I rarely do -- ever since I purchased an MXL 67G. The latter mic is about the same price, but FAR, FAR better for vocals and acoustic guitar. (I tried both at the same time for a single track...the difference is pretty extreme!)