Sig Sauer released a new variation of the M400 family today called the M400 Tread. The rifle has a 16″ stainless steel barrel (1 in 8″ twist), 15″ free float MLOK hand guard, ambidextrous controls, single stage polished / hard-coat trigger, mid-length gas system and Magpul SL-K stock.
The part number is RM400-16B-TRD 798681597765.
Specs from Sig:
Update 10-8-18: We’ve received the first shipment with M400 Tread rifles. Photos are below: