I picked up a few boxes recently and believe they are fairly new to the civilian market (I may be wrong on that). There appears to be little information about them online. My assumption is they should be interchangeable with CCI #41 and, for all intents and purposes, CCI 450s (which have a slightly modified anvil shape to the CCI #41s but seem to provide the same flame/data). But I'm wondering if anyone has done any comparisons yet or has real world experience with the Win #41s.