Both retainer products are made from copolyester, however, the density of the materials are different. Our Invisible Retainer Pro is recommended for day use as the material is slightly more flexible, making it durable and easy to insert and remove frequently throughout the day for eating, drinking, speaking, etc. Our 2inONE Night Retainer on the other hand, is slightly more dense to withstand any clenching and grinding forces during your sleep.