I had a similar query last year--wound up buying some and would advise you not to waste your money. I tried them with tomatoes and didn't find the plants did any better than the ones I put out later. I kept a thermometer inside them for a while and didn't see much difference in the temperature. I have used hotcaps to germinate squash and melon seeds, and found they work well if you are careful to water inside them. Judy Warner warner@ultranet.com zone 3-4