Easy to install, fixing holes (screws not included). Just unscrew the two fasteners to open the porthole. Also perfect for replacing the old boat porthole. Usage: 21cm pre-drilled porthole, round tempered glass opening 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 fixing holes. (screws not included), synthetic anti-corrosion fittings and durable waterproof seals. Package Contents: 1 x Boat Porthole 21cm Black RV Car Boat Yacht Round Window Spare Porthole. Features: Round porthole for boat, motorhome, etc. Simply unscrew the two fasteners to open the porthole. Easy to install, mounting holes (screws not included). Anti-corrosion synthetic fittings and durable waterproof seals. Glass is tempered for strength, clarity and chemical resistance. Features: Item Name: Boat Porthole. Material: ABS plastic. Color: black. Size: approximately 21 cm. Content: 1 boat porthole. Note: 1. Due to the lighting and different monitor settings, the item's color may be slightly different from the color shown on the pictures. 2. Measurements are taken by hand, the dimensions indicated may vary by 0.5-2 cm.