McGill Extension Ring Square 4"X4"X2-1/8" Gauge 16 is a durable electrical box extension designed for flush mounting applications. This square ring accommodates standard 4"x4" electrical boxes, extending them by 2-1/8" to align with finished wall surfaces. Constructed from 16-gauge steel, it provides reliable support for outlets, switches, and junction boxes. Ideal for retrofit installations and wall thickness adjustments, this extension ring ensures proper box positioning and professional electrical installations. Essential for electricians and contractors working on residential and commercial projects.