It's called Protekto Trim. I got it at a local KNIPPS. It's 5/8 inch wide and black. IMO the tim is the key to the clean cut. Just lay it slightly over the edge so it can turn a wavy not straight cut into the straightest looking cut and it covers up the raw edge.
Thanks for the tip! I picked one up at Harbor freight for $50 (not the one on sale).
Absolutely the cleanest cut on sheetmetal out of jigsaw, cutting wheel, and sawzal. NO sharp edges at all. Can run my finger along it. I was temted to try a nibbler too but they didn't seem thick enough.
The only hard part was controling the sucker. It just wanted to keep cutting in any direction plus the blade was a little flimsy which made control a little harder too.