I recently purchased the synthetic Kurz scabbard for my newly acquired 590 shockwave. It's a great piece, but it only fits a factory shockwave. Not enough room for accessories. Even an empty 1913 pic rail on the receiver is enough to prevent it from full insertion. Sounds dirty, but I'll leave it.
I ended up giving it to my father, who also has a shockwave, and only intends on adding the Crimson Trace green laser saddle.