Zip-off trousers are a super versatile type of walking trouser. As well as enjoying the high-wearing comfort and many functions of normal hiking trousers, you can also zip sections of the trouser legs off. One trouser leg may have 1-2 integrated zips. So, a pair of trousers with a zip on each leg can be very quickly be turned into a half-length or ¾-length pair of trousers. If there's another zip, the long trousers can even be turned into shorts. This means you can wear a pair of these, set out on a hike in the morning in cooler temperatures and quickly shorten them later in the day when the temperature rises. Likewise, you can just as quickly turn them back into long trousers if the weather suddenly worsens.