A polymer made from two or more different types or monomers; ABS plastic is a co-polymer, for example.

According to DeEnterprises' Peter DeSantis, co-polymers (acrylic powder in general) are primarily made up of two main ingredients: polyethyl methacrylate and polymethyl methacrylate. Manufacturers can manipulate the percentages of the two products to change the workability of the product. Normally the more ethyl methacrylate used in the powder, the stiffer the product is to move. The more methyl methacrylate the harder the product is. DeSantis says, "Nail technicians should know that methyl methacrylate (MMA) is only prohibited in its liquid monomer form. Polymer manufacturing is much more complex and there are many more variables however this gives a basic knowledge of polymers related to the nail industry."