These fit the K4/5 600 & 750’s, but unfortunately not my new bike 
£70 including spare tubes and shipping.
If you’re not sure what the benefit is in these, they replace the stock handlebars (clipons) and are adjustable for angle, so you can have them flatter for easier turning (so useful at the track) as you have more leverage, and the tubes are quickly replacable in the event of an off, so you can just slot in a new tube (£10) and carry on riding, unlike the stock ones which require the removal of the yokes and whole unit. They also look very tasty when installed.
