An improved mounting device for enabling a user to quickly and securely attach and detach an accessory (e.g., a scope, light, bayonet, etc.) to a Magpul MLOK rail of a firearm. In a preferred embodiment of the present invention, the device comprises an upper portion, a lower portion, and at least one locking mechanism to enable a user to quickly removably attach the improved mounting device to an MLOK rail on a firearm. In a further preferred embodiment of the present invention, the device also comprises a side wedge and side wedge spring.