The Valken SMAG 140rd mid-cap airsoft magazine is constructed of durable hard polymer material, are lightweight, and can take a beating. The 6mm AEG magazine features a standard STANAG design making it great for all types of M4 magazine pouches, and compatible with most major brand M4 airsoft electric guns. They include a stronger feed spring allowing up to 0.36g BBs to feed flawlessly, and no winding is required like hi-cap magazines. An airsoft speed loader is required to load BBs into these magazines (which is not included).