You should always consider the origin of the jacket you're looking at as UK sizes are different to European makes. Italian jackets tend to be well fitted, whereas UK and German manufacturers are more generous around the waist. If you have a wide neck, look for a collar that is adjustable and if you like to wear your gloves tucked into your jacket, look for adjustable cuffs.
Jackets are sized using chest measurement, so first off, use a tape measure to measure the fullest part of your chest. Place the tape under your arms and make sure it's flat across you back in order that you get the most accurate measurement possible. It's always worth remembering, however, that if your belly extends further than your chest, you'll also need to take that into account.
Take a little time to think about which style you fancy. Leather jackets offer more abrasion protection but won't be waterproof and can be quite heavy. Textile jackets are often waterproof, but can be baggy on a sportsbike. Short style jackets are good for sportsbikes as they won't ruck up at the front, while longer jackets suit touring and upright bikes, keeping your waist warmer. If you want to ride all year round look for one that has a removable thermal lining, so you can wear it through hot and cold rides.
It is good to have CE approved armour in the shoulders and elbows, but also see if it has a CE back protector, or at least a pocket to take one.
Take your time to make sure it's right, it's important that your jacket fits well. If you do need to send it back, remember that we offer a 365 day returns policy.