Depends what diameter your steerer is? I'm guessing this is for 1"1/8th steerer, and it says on the stem for 31.8mm bars (so the "newer (fatter)" standard, but not the "newest new" standard of 35mm.... if you see what I mean?) standard oversized mtb bars.
It fits a standard 1 1/8 steerer and takes 31.8 bars, probably the most common bar size these days - however, shims can be bought on eBay if you wish to use 25.4 size bars
Urm... Not renthal bars, I do however have a set of wide black flat (bit of sweep) kona branded bars which are in the garage doing nothing.... They would bump the postage up I expect, £10 more and I'd chuck them in with the stem?