Whizzer "people"chain
Hi Ren, it is Standard cruiser bike chain sized. I like Continental Chains, that sell cheap under the "KMC" brand name.
Whizzer chain is also available, a "Half Link" is a special link that allows the user to remove (or add) 1/2 inch of chain at a time instead of the normal 1" at a time . This is because there are 2 types of link in your chain, an "inner" roller type and an "outer" flat-leaf with the axles on it. A standard link change is one of each equalling one inch of chain, being 1/2 inch of wheel movement.
Whenver possible, under ANY circumstances I ALWAYS use a full link.
I think I have some 1/2's other dealers may, and Whizzer should also.
I hope this "Chain 101" helps you.
Mike