I purchased two packs of Estes E12-4 engines online. Of the six engines three worked fine, Estes instructed me to destroy one and two of them CATOed. One of the CATOs destroyed my rocket and the on board camera. I have a third pack that I purchased from a brick and mortar store. I would rather throw them away than risk having another rocket destroyed. So far Estes made good on the first CATO that did not damage my rocket. I am confident that they will make good on the second CATO. They have done so in the past.