Virtually unbreakable polycarbonate construction, high structural rigidity, long-term form retention. 0.375 in longer and wider on all sides than standard to cover large wallboard openings, assures NEC-required gap coverage for most wallboard-to-box openings. Screw-catch feature holds color-matched plate mounting screws captive for ease of installation. Superior abrasion and impact resistance. Temperature rating of -40 to 65° C. Meets flammability requirements per UL 94, V2 rated. UL 514D and cUL Listed. Meets all CSA requirements. Mid-size - 4.875 in x 6.75 in