Had the opportunity the check out the Seiko Prospex Kinetic GMT divers at K2 recently. The three models I handled are SUN019P, SUN021P and SUN023P. They are big, thick and heavy, and will dwarf almost any Seiko diver you put next to them except the big tunas (SD and Emperor). They are powered by the 5M85 Kinetic movement and the GMT hand can be set independently.
I do not know the diameter but I do know that the lug width is 24mmm. Here are the pictures I took.