I have heard that you to have a strong honey flow going for them to use those. I have been curious to try them myself but have not yet, mostly cause of the $ side of it. As I build up my numbers, most of the money I make right now is just reinvested back into more equipment and that $100 buys either 2 tb, 2 bb, 2 hive bodies and 20 frames/foundation, or 3 hive bodies and 30 frames/foundation. I thought I was going to stop doing extractions after this last one is completed, I'll have my $ for my extractor, but the bees have other plans and need more supers.