These slides are different that the slide they are building now. They are 5oz heavier and were discontinued at least 5 years ago. It was way before Glock brought out the model 41. I don't think they built a 21 slide in the heavy weight. Lone Wolf is building a Gen 4 G41 slide but it isn't a heavy slide. It would work for a 45 Super with a Barsto extended G41 ported barrel. Here is a link to the slide: https://lonewolfdist.com/alphawolf-slide-g41-45acp-gen4-replacement/