Installed this (it was a day late of guaranteed delivery date) along with a 16 tooth sprocket and X2 chain. 75mph feels like 55mph vs stock drive ratio. I have JT chain and sprockets on my DR650 too and have no complaints.
I wanted to drop 1 tooth on my rear sprocket on my 2009 KLR650. I already put a 1tooth bigger sprocket on the front. Stock on the rear is 43T and I went with a 42T sprocket. I was just trying to get the engine to a sweet spot at 65mph!