These chair seat cushion covers are extremely well made; have exceptional fabric; stretch for a custom fit; and I believe are waterproof. I bought these to cover seat cushion foam, which I purchased separately on Revain, to use, e.g., atop a wheelchair seat, recliner seat, car seat, etc., for better comfort. The seat cushion foam is also available on Revain in different sizes (e.g., 16 x 16, 18 x 18), and these chair seat cushion covers stretch to fit over both the 16" square and 18" square cushSee full review