A boss kit is needed to bolt the wheel onto the steering column and allow the horn to still work, with the standard wheel the boss and the steering wheel are combined as one unit.
That one looks okayish, but a little garish for my tastes.. Simple designs look better IMO . Go with a momo / sparco or even a saas /autotechnica one from the likes of autobarn (or ebay). The more expensive ones are better made with higher quality materials, so paint wont flake off, rust, will be real leather etc... and also are engineered to design standards.
Important to note ADR10 relating to steering wheels, basically you can only go as small as 35cm in diameter as you still need to be able to see your gauges. I have a 32cm momo wheel and got defected for it. Its still on the car because i like it too much