The H1's silicone strap was designed specifically for the watch. It's comfortably supple, easily adjustable, and fits tightly into the lugs for a smart, smooth finish. It ships with a stainless steel clasp.
It comes in one size and is adjusted by cutting away sections until you have the length you desire, so be careful not to remove too much at once. The clasp allows for micro-adjustment, meaning you should be able to get the perfect fit for your wrist.