Geissele M-Lok Hk Hk416 Rail 14.5in Black. The rail system utilizes the stock HK barrel nut but incorporates the strength rigidity and modularity expected of a Geissele product. Specifications for Geissele AR-15 M-Lok Hk Hk416 Rail: Manufacturer: Geissele Gun Model: AR-15 Gun Rail: M-LOK Handguard Material: 6061 T6 Aircraft Grade Aluminum Mount Type: M-LOK Package Contents: Geissele HK416 Super Modular M-LOK Rail What firearm models does the manufacturer say Geissele AR-15 M-Lok Hk Hk416 Rail is compatible with? The manufacturer says that Geissele AR-15 M-Lok Hk Hk416 Rail is compatible with AR-15Geissele 05-848B: M-Lok Hk Hk416 Rail 14.5in Black