If you've ever wondered why a strap you purchased doesn't fit into the slot of a deployant buckle, wonder no more.
A strap for a deployant buckle needs to be 2mm or less in thickness to work on a deployant buckle. It can be 4 or 5mm thick higher up the strap where it connects to the watch but you can't have any padding at the holes.
A strap for a tang buckle can be any thickness (with-in reason) and there are no worries. But, if your strap won't fit into your deployant buckle, then it was made for a tang buckle.