GLOCK 31C 357 Sig 4 Slide. This will work only with Gen4 pattern full size frames, such as the 17, 22, 31, 34, 35, 37 or LWD. Glock had not made these in over 10 years and they recently made a small batch.
Get one while you can. This will not fit gen3 pattern frames. OEM GLOCK 31-C Gen4 Complete slide with barrel and recoil spring assembly.