ProMag Roller Follower Lined Rifle Magazine AR-15 5.56mm 40 Round Black 1 Pack DuPont Zytel Polymer 40RD. It is constructed of DuPont Zytel polymer with anti-tilt mag follower and mag spring formed from chrome silicone wire. Specifications for ProMag Roller Follower Lined AR-15 5.56mm 40 Round Rifle Magazine: Manufacturer: ProMag Color: Black Fabric/Material: Polymer Magazine Capacity: 40 Round Caliber: 5.56x45mm NATO Gun Make: AR Platform Gun Model: AR-15 Package Contents: ProMag Roller Follower Lined AR-15 5.56mm 40 Round Rifle Magazine What firearm models does the manufacturer say ProMag Roller Follower Lined AR-15 5.56mm 40 Round Rifle Magazine is compatible with? The manufacturer says that ProMag Roller Follower Lined AR-15 5.56mm 40 Round Rifle Magazine is compatible with AR-15ProMag RM40SL-40RD: Roller Follower Lined Rifle Magazine AR-15 5.56mm 40 Round Black 1 Pack DuPont Zytel Polymer