I'm just wondering if anyone has used this jet kit. I've been told not to use anything other than genuine Keihin jets, which I don't think these are. Opinions appreciated.

 

Physically they should be fine, id just be curious as to the marking on them, if they corespond to kiehin or something else. You could measure them and compare it to the charts to see if the numbers are good. You could fire off a question to the seller, and ask him the origins and sizes, and if theres been any complaints.
Its just like, youre not supposed to use ink jet carts for the epson printer which arent genuine, but when the cost is much less, its hard not to.
Jets are just pieces of brass, with threads on the outside, a certain length and a precision hole in the middle...they arent that tough to make.