Yes they are a form of half check. They tend to be material or leather for the main part with a loop of material that 'runs' to reduce the collar size when the dog pulls. 

Ah well there you go, said I would be wrong didn't I! ;)

Hi,
I bought Bob a Halti harness at the weekend. Its fantastic! I had tried everything previously to stop him pulling but he just wouldn't give up. This new harness - a martingale type i beilive from previous posts - has stopped all that, best of all he no longer gets blood shot eyes and has more energy to play when let off the lead!