These small compasses slide onto the strap of your military watch and are ideal for orientation and plotting a route.
Even in these days of Satnav's and phones with GPS there are lots of times when you won't have a Satnav with you or in the case of a phone can't get a signal.
Having used one of these little compasses myself I find it's surprising how often a traditional compass can come in useful - not only that but it looks good on the strap as well and is a low cost addition to any military watch.