This sentence is not entirely clear, but it seems to be saying that they produce crystal drinking glasses in a passive voice. The correct translation of "в страдательный залог" in English is "in the passive voice." So the sentence could be rephrased as: "Crystal drinking glasses are produced by them in the passive voice."
This sentence is not entirely clear, but it seems to be saying that they produce crystal drinking glasses in a passive voice. The correct translation of "в страдательный залог" in English is "in the passive voice." So the sentence could be rephrased as: "Crystal drinking glasses are produced by them in the passive voice."