Is it safe for guinea pigs wear collars?

no i wouldn't put a collar on a guinea pig because..(toys and cage bars) can get caught and the guinea pig could strangle but putting on a harnnes is a tottaly different thing its when you take your guinea pig out for a walk but they lead you if you pull they could die of suffecation and when you are finnished with the walk you should take it of when putting them back in the cage and 1 thing you should seriously know with harness and collars don't lead them in the streets because they can easily slip out of them