Last year when we built our Texas Prepper Greenhouse I sort of cheaped out on the plastic and boy did we pay the price for it. By August the skin was in tatters, by the middle of October it was all over my garden area. What a mess! Yup, I got the 3 mil that they had at our local farm store even though the instructions said to get the 6 mil. If you build this greenhouse GET THE 6 mil.