This is the Lancer A5AWM 10 round magazine for .223 and 5.56x45mm AR rifles.
Lancer Systems developed their L5 Advanced Warfighter Magazine (L5AWM) to have the weight benefits of a polymer magazine with the durability of steel, by having one piece wrap around steel feed lips combined with a durable polymer body with an easy to grip surface texture.
They are very durable and ideal for use in challenging weather conditions.
Compatible with all AR15 and STANAG formats including AR15/M4, HK416 and SA80.