Easy to install, mounting holes (screws not included). Simply unscrew the two closures to open the porthole. Also perfect for replacing the old boat porthole. Usage: 21cm pre-drilled porthole, round opening tempered glass for boat, yacht, motorhome, car, tourism. Corrosion-resistant synthetic fittings and durable waterproof seals. Glass is tempered for strength, clarity and chemical resistance. Easy to install, pre-drilled countersunk mounting holes. (screws not included), anti-corrosion synthetic fittings and durable waterproof seals. Package Contents: 1 x 21cm Black Boat Portlight for RV, Car, Boat, Yacht, Round Window, spare porthole. Features: Round porthole for boat, motorhome, etc. < p>Simply unscrew the two closures to open the porthole. Easy to install, fixing holes (screws not included). Anti-corrosion synthetic fittings and durable waterproof seals . Glass is tempered for strength, clarity and chemical resistance. Features: Name of item: boat porthole. Material: ABS plastic. Color: black. Size: about 21 cm. Contents: 1 boat porthole. Note: 1. Due to the lighting and individual monitor settings, the item's color may be slightly different from the pictures shown. 2. Since measurements are taken by hand, the dimensions indicated may vary by 0.5-2 cm.