-Upper body, arms and waist POC Storm Shadow (neck cut down for size)
-Chest strap 25th / ME Ninja Ku
-Sword ROC SE
-Legs 25th / ME Red Ninja
-Head 25th / ME Red Ninja
-Shoulder pads ROC Flash
-Hood Resolute Zartan
-Arm Guards POC Firefly clipped down
-Spine...custom dremelled spine from ROC Cobra Commander body

For those not familiar with Sei Tin, he's from the DDP comic run of G.I. Joe and popped up at one point running the Red Ninjas...he also had his spine replaced with a cybernetic one by Cobra when injured.

I've always wanted a figure of this character since I've seen him mostly because it finally gave the Red Ninjas someone to act as a leader...aside from the interim leaders that were tacked onto the clan, like Firefly or Slice and Dice.