If you have a watch on the larger side look at other NATO straps. This Tech Swiss one has a secondary strap that is only about 8cm. After doing a bit of research, I've found that other brands average around 11cm. I considered sending it back, but instead I've cut the secondary strap off; effectively making it into a Zulu watch strap. Just for your reference, my watch is 44mm from pin to pin.

Update: I should also mention that the description says "Length of Band: 12" Including Buckle". The strap that was sent to me is only 11 3/8". Maybe they sent me the wrong strap??