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 7.62x51 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(R) system, provides a fast round-count estimation without affecting the durability or reliability of the magazine. Like our 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 also 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.