Geissele MK15 HK416 Super Modular M-LOK Rail 10.5in Sand 10.5in. The rail system utilizes the stock HK barrel nut but incorporates the strength rigidity and modularity expected of a Geissele product. Specifications for Geissele MK15 HK416 Super Modular M-LOK 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 MK15 HK416 Super Modular M-LOK Rail What firearm models does the manufacturer say Geissele MK15 HK416 Super Modular M-LOK Rail is compatible with? The manufacturer says that Geissele MK15 HK416 Super Modular M-LOK Rail is compatible with AR-15Geissele 05-827S: MK15 HK416 Super Modular M-LOK Rail 10.5in Sand 10.5in