This is a Lancer known as the Magazine Cinch, model 999-000-1350.
The Lancer Magazine Coupler was developed for the L5" L5A and L5AWM Translucent Magazines. Ensures that the magazines are aligned and held securely without obscuring the view of the rounds. Also compatible with USGI Aluminum and Steel Magazines.
Features:
Fits L5, L5A and L5AWM Translucent Magazines
Fits USGI Aluminum and Steel Magazines
Does not Obscure View of the Rounds in Lancer Magazines
