Please be warned about so called internet special offers. Right now, there are motorcycle-helmets available on the internet, that do not fulfill the European regulations, even if the relevant pages explain the opposite. This can lead to big problems with the insurance company after a crash.
For example, if you order a SHOEI helmet in the USA, this helmet does not meet the European regulation ECE 22.05. Every SHOEI sold in the USA has a DOT certification or a SNELL/DOT certification. As mentioned, this could lead to serious problems with insurance companies and the police. Furthermore, the weight of these helmets is significantly higher than the weight of European certificated helmets (see table). This could turn a special offer into a expensive mispurchase.
Therefore we advise to buy motorcycle helmets only at a specialized store.
If you nevertheless decide to buy a motorcycle helmet over the internet we advise you to check the ECE homologation and the possibility to change the helmet if the size is not right. Also check the availability of service and spare-parts.