It is thinner and more comfortable, sizing is not overly generous and its very comfy once on.
The cuffs can be problematic if you wear Rukka gear as the cuffs on the Rukka jacket lie over the top of the knitted cuff of the J501 and then you have to somehow get your gloves inside aswell.
Thats not an issue with the J501 in particular just a fact with most inner jackets and the Rukka inner cuff system. Some people cut the knitted cuff off the J501 so it sits further back up the wrist allowing the Rukka cuff and gloves to fit better.
It does get mega hot when switched on though and if you are serioulsy riding in all weathers throughout winter then on the days I needed it it kept me going.
I think its the best heated jacket on the market having tried a few. I wore it on some real cold daysin the minus temps and travelling at very high speeds so the wind chill was ffing cold to say the least.
With the heated grips and the jacket on low setting I was on the warm side of comfy, on hot setting I was nearly passing out with the heat.
Stock might be an issue though as Keis are renowned for only making a set amont and then when they sell out there gone and they dont make anymore, dont suppose Covid will have helped matters. If you can find one in your size then I wouldnt hesitate.
