I've worn HK hair extensions since they were known as Headkandy and sold on their own site by the same name. In the last few years they've moved over to dirtylooks.com but the quality hasn't changed, they're the nicest extensions I've ever worn and are lovely and thick.
As my hair is naturally so thick I have buy two sets at a time; what I'm wearing at the moment is just under two, as I cut the ones I was wearing at the top of my head to blend in with my layers, and they're too short now that my hair is finally growing. My hair is naturally just past my shoulders, and I wear the 16-18in extensions.
I can't wear extensions straight because they don't blend well with my natural hair if it's humid and starts going a bit frizzy, but I was getting bored of just wearing them waved with a wand all the time, so I dug out my Sleep in Rollers and thought I'd give them a try.
There's two ways I use them on my extensions, and I love both effects.