A 10/30 Magpul PMAG refers to a type of magazine designed and manufactured by Magpul Industries. Here's what the term typically means: Capacity: The "10" in "10/30" refers to the magazine's intended capacity, which is 10 rounds. This means the magazine is designed to hold up to 10 cartridges or rounds of ammunition. Compliance: The "30" in "10/30" indicates the physical size and shape of the magazine. Originally designed to hold 30 rounds, a 10/30 magazine is modified to restrict its capacity to 10 rounds. This modification is often done to comply with firearm regulations in certain jurisdictions that impose restrictions on magazine capacity. PMAG: "PMAG" stands for Polymer MAGazine, indicating that the magazine is made from polymer (plastic) material rather than metal. Magpul PMAGs are known for their durability, reliability, and lightweight construction. In summary, a 10/30 Magpul PMAG is a 10-round polymer magazine that is modified from its original 30-round design to comply with legal restrictions on magazine capacity in certain areas. These magazines are popular among firearm owners who need to adhere to capacity limits while still using high-quality, reliable magazines..