"Transparent plastic" refers to a type of plastic material that allows light to pass through it easily, making it see-through or clear. Full definition
It's top part, through which we can see the text, has made of transparent plastic. (e-ink-reader.ru)
To make it easy to observe the bees as they came and went, the colonies were housed in boxes connected to the outside world by transparent plastic tubing. (newscientist.com)
I develop the paintings from studies made from transparent plastic color sheets. (mocajacksonville.unf.edu)