It's rare that any of us throw on a jacket that's purely designed to keep the rain out; because modern rain jackets are usually capable of much more than 'just' being waterproof for sports activities, leisure or travel. Nowadays, waterproof, unlined jackets are often called hardshells – but what makes a hardshell a good rain jacket? According to the Swiss EMPA, a hardshell is waterproof from a water column of 4000 mm. But, if you're going to be active in your jacket you'll need to pay attention to its breathability too. After all, what good is a waterproof rain jacket that gets wet on the inside during moderate exercise? If you're really only interested in rain protection, you'll also find simple models that serve this purpose for little money.