Corrugated plastic sign boards. There's not much to say about them but these were the perfect size to clip to the sides of our guinea pig's habitat so he can't spray everything within 4 feet of his cage with urine. It wasn't an issue for our usage, but a couple of them had chipped corners which may not be ideal if you are using them as signs or as components for another project. I don't know if that is avoidable by any means other than picking them up yourself. Locally, nobody had this size.These are great signs only problem is the pink is much lighter than the photo. Very light. Only returned it because I was looking for a dark pink.Ran out of the yellow we bought so my husband has to get extra - but we used this as the base for the lower and upper levels! We now have happy spoiled guinea pigs!I ordered 2 boards which are slightly different sizes but it gets the job done. I use it as a floor for underneath my guinea pigs cage. It is completely water proof.This product will work for what I need it for.Bought to make fundraising yard sale signs to be put out on the highway for a week before the sale. We needed waterproof and sturdy and bright and these fit all those perfectly. They fit onto a standard plastic sandwich board. There was some variance with the sizes, one or two out of ten weren't perfectly straight but it was fine for what we needed.Worked great with vinyl letters. We plan on using them for many years.I ordered these through someone else and they were sold out, so I went this route. I choose the measurements for a reason and 4 of them were useless because they were a 1/4 to 1/2 inch off!Picture looks bright pink. Actual item was salmon pink. It served the purpose but I wasn’t expecting that color.