The PMAG 20 LR/SR GEN M3 Window is a lightweight, cost effective, highly reliable 20-round magazine for SR25/M110 pattern rifles chambered in 7.62×51 NATO (.308 Winchester). Constructed from next-generation impact and crush-resistant polymer, the new magazine features durable, dual-side transparent windows which allow for a quick count of the approximate number of rounds remaining in the magazine via a high visibility indicator coil on the spring and numerical markers on the magazine body. This proprietary capability, known as the MagLevel system, provides a fast round-count estimation without affecting the durability or reliability of the magazine. Like their other PMAGs, the 20 LR/SR GEN M3 Window magazine features a stainless-steel, corrosion-resistant spring and an anti-tilt, self-lubricating follower. The magazine’s lines follow a constant-curve internal geometry for continuous reliable feeding. The low-profile ribs and aggressive front and rear texturing help give shooters a positive grip for magazine changes in all environments. A paint pen dot matrix at the bottom panel of the body allows easy marking by the end user for identification purposes. Other standard features include a flared floorplate that aids extraction and handling of the magazine; this flared floorplate also improves drop protection and is slim enough to ensure better compatibility with tight double magazine pouches. The magazine is also simple to disassemble and makes for easy cleaning and maintenance when necessary. Designed specifically for SAAMI-spec ammunition, the PMAG 20 LR/SR GEN M3 Window is less than half the weight of standard issue steel magazines and maintains a service life round count approximately equal to the rifle barrel itself. Accessories designed for the 7.62X51 NATO line of PMAGs are also compatible with the PMAG 20 Window.