Better than OEM replacement Additional UV protection molded into the plastic to stop yellowing Includes pre-applied butyl sealant for both door and window seals Window held in place by frame and butyl only, use caution when handling the glass Includes both inside and outside pieces Window opening: 12" x 21" Glass sold separately. Installation screws not included; use #6 flat head x 1-1/2" length. Needs 16.