To date X-Products has released 8 variations of their drum magazine. Some of their drum magazines work with our lower, while some do not. This is due to the height of their magazine tower. Their tower is optimized for use with forged SR-25 lower receivers such as the KAC SR-25. Many billet lowers can have different variances in regards to the mag well length. We are working with X-Products to ensure that future production of both of our products will work flawlessly together. X-Products has modified a number of our lowers that you can purchase directly from them that is pre fit to their current production drums. All other SR25/M110 type magazines will still work in our lower. However we recommend that you modify the magazine (drum) since it is a consumable product and fitment issues might occur in other systems as well. If you have any further questions in regards feel free to send us an email.