<a href="https://en.wikipedia.org/wiki/Roller_chain" class="extiw" title="wikipedia:Roller chain">Roller chain</a>, used to transmit power in motorcycles and bicycles.  Photo shows two different sizes.
<bdi><a href="https://www.wikidata.org/wiki/Q15080600" class="extiw" title="d:Q15080600"><span title="German civil engineer and photographer">Ralf Roletschek</span></a>
</bdi>
<span class="int-own-work" lang="en">Own work</span>