Difference in horseman rangefinder cams? 180mm vs 18cm

Hi,

Does anyone know if the extra hole makes any difference? Only compatible with certain cameras? The screenshot was too big so here is a link to eBay auctions where the cams in question are visible,

180mm with hole
http://www.ebay.com/itm/Cams-cam-of...226154?hash=item5d698423ea:g:J1sAAOSwmLlX92Zj

18cm without
http://www.ebay.com/itm/Cams-cam-of...948409?hash=item1a1d40fe79:g:OvIAAOSwYIxX92WF