I have 3 models of Pactimo bibs: Ascent Vector, Summit Raptor, and Summit Stratos. At 6'-1" and 170#, the medium is a perfect fit . There is a substantial difference in chamois between Ascent Vector and Summit Raptor "12-hour". But I was a bit surprised that there wasn't a greater difference between Summit Raptor and Summit Stratos. While I appreciate the improved design, I was expecting a bit more density in the Stratos padding. Still, a very well thought-out design all around, as they've been very comfortable for a couple 60 mile rides now. I'm planning to use them on next weeks 158-mile "Bone Ride", led my former 7-Eleven racer, Tom Schuler, and the 180-mile "Ride Across Wisconsin" in July.