New out this year Konus Pro Atomic T-1 style sight. The same sight as the New Sig Sauer T-1 style RD sight. The Konus has a more durable mount and cost less. I don't know how well they will hold up on the UltiMak gas tube rail because it gets very hot. On an UM it will co witness with the irons. They run about $100 and mine has held up well so far.
Here are pictures.
GC