Softer throttle spring. Here’s a vid someone else put up. I just put this in my bike. Seems ok. I gotta ride with it to see how it works. It’s supposed to help with arm pump etc. https://www.tworide.net/product-pag...a-xtrainer-all-years-and-250-300-rr-2016-2017 My bike is a 2015 but the 2two. spring is softer than mine. It’s for the oil injection bikes but I was wondering how much lighter the spring might be..so I tried it to see..