So I gave my flat tip-ups to my son this year and decided to go to one ret of rounds along with my Indian Hill set. I read a lot of posts on here on the difference between the Frabill's and the HT's and now can say without a doubt don't buy the HT's. The ones I bought are called "extreme thermal" but there is no insulation on the bottom side like on the Frabill's. I wondered how they would prevent the holes from freezing and I got my answer today...THEY DON'T. I ended up having to use hole covers as before them I was skimming the holes under the HT's all morning! Also the extendable flags are very weak. Two of them broke when folding them back. The Frabill's with the foam insulation on the bottom of the tip-ups never froze up all morning. I replaced the smaller flags with their longer flags that I bought. Those flags are a little bit of a pain to set up but once they are setup they were great.
