The crush point shows the amount of weight a flue liner can withstand before it is crushed. In plain speak, differentiates the flimsiness or low quality liners from the quality made chimney liners. Out of the chimney liners we tested, there was one chimney flue liner that stood out from the others. It was the Flex King Pro with a crush point of 560 lbs. The second runner up was the Flex King chimney liner with a crush point of 300 lbs. The Flex King Pro seemed to be made the best by looking at the overall construction compared to the other liners we tested.