Castelli just make good products. Fits perfectly XL 5 11 170 lbs little loose in the wast but I prefer less tightening fit. No flapping so must be a good fit. Get a size smaller if you want a tight fit.
This is my fave all purpose top, from MTB to Road rides to Triathlon training rides. I appreciate the Castelli graphic design, sharp, stylish but never too flashy, trendy or obnoxious. This shirt is comfortable, breathes very well has excellent storage and length in the back and the sleeves are snug. Great Castelli Quality. On sizing I do need to size up a full size as they run small vs. US Men...IMHO.
I wear this jersey on almost every ride (2-3 rides per week; 25-70 mile rides). It fits like a second skin; is light, flexible, and so comfortable. Not the cheapest jersey you can find but one of the best. Refer to the sizing guide for fit.
I own several Castelli jerseys. I prefer them for the feel of the materials they use. This particular jersey fits a little looser than the other Castelli's I own. And that's fine. It is still form fitting enough and is not restrictive in any way. It feels like a jersey I can use when I'm a bit more casual about my ride.
Lighter fabric which is ok. Sleeves not as tight as Prologo V but longer. Does not have the small zip up pocket in back for keys. Overall, I like the Prologo V better than the Prologo VI.
I have been wearing the prologo jersey for the last several years. It is a club fit, but runs small. I really like the longer sleeves and jersey on this latest version. I find it flaps around less at high speed and is more comfortable. These jerseys breath well. As with all Castelli products they run 1 to 2 sizes smaller than other brands.
The overall quality of the jersey is good at the price point. I was hoping the Prologo VI jersey would have sleeve lengths similar to the Prologo V, but no. I guess I need to pay better attention to the pictures to realize which are normal bicep length and which ones are either to or past the elbow. I guess on cooler days the longer sleeves are a plus but otherwise they tend to bother me curling up around the elbow. Regardless I would however probably buy the gray one if I see it on sale.