ProMag Rifle Magazine AR-308 .308 Winchester 40 Round Black 1 Pack DuPont Zytel Polymer 40RD. It is constructed of DuPont Zytel polymer with injection molded mag follower and mag spring formed from chrome silicone wire. NOTE: This item is not compatible with rifle using Armalite pattern magazines. Specifications for ProMag AR-308 .308 Winchester 40 Round Rifle Magazine: Manufacturer: ProMag Fabric/Material: Polymer Magazine Capacity: 40 Round Caliber: .308 Winchester Gun Make: AR Platform Gun Model: AR-10 Condition: New Package Contents: ProMag AR-308 .308 Winchester 40 Round Rifle Magazine What firearm models does the manufacturer say ProMag AR-308 .308 Winchester 40 Round Rifle Magazine is compatible with? The manufacturer suggests that ProMag AR-308 .308 Winchester 40 Round Rifle Magazine is compatible with AR-10ProMag DPMA4-40RD: Rifle Magazine AR-308 .308 Winchester 40 Round Black 1 Pack DuPont Zytel Polymer