This is the 14775th most frequent Russian word.
пластиковых
"Пластиковых" means "plastic" (adjective, plural or genitive singular).
In this sentence, 'пластиковых' is used as an adjective to describe the material composition ('plastic') of the item ('glasses'). The form, 'пластиковых', agrees in gender, number, and case with 'бокалов' ('genitive plural').
Я выбрал пластиковых бокалов для вечеринки.
I chose plastic glasses for the party.
Here, 'пластиковых' modifies the noun 'изделий' ('items'), showing the material is plastic ('genitive plural'). It indicates the type of products sold in the store.
В магазине продают широкий ассортимент пластиковых изделий.
The store sells a wide range of plastic items.
In this example, 'пластиковых' is an adjective describing 'труб' ('pipes'), indicating the material composition is plastic ('genitive plural').