Aqua One Aquis 500/700, Advance 550/750 & Nautilus 600/800 O-Ring (10698) Restore a dependable watertight seal where the original sealing component has deteriorated. These can become brittle over time therefore we suggest keping a spare to avoid any downtime Easy to Fit... $17.88 RRP $22.95 $17.88 Points Quick view add to cart