Arisaka Defense Indexer Geissele SMR 416 Heckler & Koch HK 416 Black. If you have the new MK15 416 handguard with M-Lok slots then you should use the M-Lok version of the Indexer. The Patent Pending Arisaka Indexer is a continuation of our low profile minimal control accessories. It was developed due to end-user demand for a Geissele SMR 416 version of our Finger Stop for Picatinny rails and features a slim front-to-back profile and slight radius across both faces. The Indexer can be used in a variety of ways but the main intent is to place it between two fingers (usually index and middle). This typically places it further forward on the handguard which also means it doesn't get in the way when transitioning to kneeling or prone shooting positions where most people move their support hand towards the rear. Used in this manner the Indexer makes it much easier to pull the rifle into your shoulder and maintain control while shooting. Additionally the wider flatter profile of the Indexer functions very well as a hand stop or barricade stop and also works as a forward limit to prevent your fingers from slipping off shorter handguards onto a hot barrel or suppressor. Specifications for Arisaka Defense Geissele SMR 416 Indexers: Manufacturer: Arisaka Defense Color: Black Finish: MIL-A-8625 Type III Hard Coat Anodized Gun Make: AR Platform Heckler & Koch Gun Type: Rifle Gun Model: Heckler & Koch HK416 Fabric/Material: 6061-T6 Aluminum Length: 2.2 in Width: 0.58 in Height: 1 in Weight: 0.9 oz Mount Type: M-LOK Gun Rail: Picatinny Country of Origin: USA Features of Arisaka Defense Geissele SMR 416 Indexer Requires an IP25/T25 Torx wrench for installation (not included) Package Contents: Arisaka Defense Geissele SMR 416 Indexers Arisaka Defense IDX-G416: Indexer Geissele SMR 416 Heckler & Koch HK 416 Black