Kayak roof rack carriers

I need kayak holders for my Rhino Racks and instead of going for $150 ones at the shops I'm considering the ones on eBay which are about $50-80.

Has anyone had experiences with these... solid and do the job, or dodgy and avoid?? Here's some links:

Uhapi brand (the name doesn't fill me with confidence): www.ebay.com.au/itm/191416165273?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
BlackHawk brand: www.ebay.com.au/itm/121391977284?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
www.ebay.com.au/itm/221358477318?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
http://www.ebay.com.au/itm/121289865519?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Thanks

I will try them out... Ones at Roof Rack city start at $240... Yikes