The Seiko Monster is probably the Seiko watch with the most number of variants and has been feature many times on this blog. As we know, the regular Monsters come under the Superior line and are powered by the 4R36 movement. This time round, Seiko decided to release new variants under the Prospex line. These variants are not much different from the Superior ones except they had the Prospex logo on the dial and caseback.
Here are some photos of the SRP581K.