The fit in the can is very tight, almost an interference fit, and I had to clean out some of the carbon / soot to get them in.
As with the others they do need a hole drilled for the retaining bolt, but I have to say the construction quality is excellent.
A quick test at 3/4 redline brings the noise below 95dB (without I'm reading 118db!!!!) at 1m(ish). Should save me lugging standard cans to trackdays at Castle Combe and Goodwood now...
Total cost under £35 (51 euro's) delivered in a couple of days.