This Sig Sauer P365 Factory 10 round .380 magazine and MTX .380 Plus 3 combo provides you the ultimate 13 round extended magazine for the P365 380. We started from scratch on the magazine internals after we released the 9mm cousin to this product. In doing so we created all custom components specific to the 380 caliber. This included the: spring, follower and the spring button / spacer. If you own a P365 380 you can now enjoy the ideal ergonomics that come with the best extended magazine for the Sig 380 P365 pistol. This is a huge upgrade from the 12rd factory option with dramatically improved ergonomics. Please note this only works with P365 .380 standard frames. Patents: US 11,408,697 B2 and US 11,168,954 B1 WILL NOT SHIP TO CA, MD, MA, NJ, NY, DC, CT, HI, WA or INTERNATIONAL.