Chain and sprocket.

[Fazerider]

3 1/2 yrs and done 38,000 miles? Your keen
Did you fit the above set? Did you come across any issues while fitting it?

To be fair, 90% of that is commuting mileage. And all but a tiny fraction of the journey is covered by Gatsos and average speed cameras so the bike doesn't exactly get thrashed these days.
I was lucky to find the set at a bargain price on eBay, IIRC I paid less than £80. 
I think a dealer was clearing old stock from his shelves. No problems with fitting, it's a straightforward job.