As long as your container is clean, they will stick. Once in a great while, I will get a jar that must have some kind of residue in it. I know as soon as I use the wick sticker as I give my wick a little tug after placing/adhering the wick. It will come loose then if there is a problem.
I've bought from a few different companies. Northstar Candle has free shipping, but most candle supply companies have them.
GoldieMN