The same SIG principles that guided its other rifle products, such as SIG516 and MCX Virtus, are present in the M400 Tread. The SIG Tread is a no-nonsense AR rifle. A collapsible buttstock is easily adjustable for length of pull and/or transport. The M400 Tread is one of lighter AR versions on the market, especially considering that it features a full-length rail and stainless steel 1:8 twist 16-inch barrel. It weighs in at a svelte 7 pounds. SIG machines the low profile micro gas block found in Tread from stainless steel. It is much lighter than standard low profile gas blocks, helping to shave weight from the rifle and keeping it balanced properly. SIG used a mid-length gas system for a smoother recoil impulse. Ambidextrous controls are another nice touch with the base M400 Tread rifle.