ERGO Grip Mossberg 500/590 M-LOK Rail Forend Black. Machined from 6061-T6 aluminum this is an extremely light-weight and low profile forend. ATTN: Mossberg uses two different length slide action bars on the Shockwave model. One measures 5 13/16" and the other measures 6 15/16". You need to confirm the length of you particular model prior to ordering. If yours measures 5 13/16" use part # 4256 and if it measures 6 15/16" use part # 4872. Specifications for Ergo Grip Mossberg 500/590 M-LOK Rail Forends: Manufacturer: ERGO Color: Black Finish: Hard Black type III Anodized Fabric/Material: 6061-T6 Aluminum Gun Make: Mossberg Gun Model: Mossberg Model 590 Mossberg Model 500 Handguard Length: 6.94 in Gun Rail: M-LOK Included Accessories: 3 Black 4332 M-LOK Rail Covers Condition: New Mount Type: M-LOK Gun Type: Shotgun Quantity: 1 Features of ERGO Grips Mossberg 500/590 M-LOK Rail Forend: Mossberg 500/590; 6 15/16" length; M-LOK Includes 3 black M-LOK rail covers Package Contents: Ergo Grip Mossberg 500/590 M-LOK Rail Forends Includes 3 black M-LOK rail covers What firearm models does the manufacturer say Ergo Grip Mossberg 500/590 M-LOK Rail Forends is compatible with? The manufacturer suggests that Ergo Grip Mossberg 500/590 M-LOK Rail Forends is compatible with Mossberg Model 500 Mossberg Model 590ERGO Grips 4872: Mossberg 500/590 M-LOK Rail Forend Black