The Polypipe NS45W 21.5mm 90° ABS Knuckle Bends are a pack of 10 waste pipe elbows designed for use with storage tank water heaters. Manufactured by the trusted brand Polypipe, these knuckle bends are durable and reliable for connecting pipes in your heating system. The 90° design ensures easy installation and efficient flow, making them an essential component for any heating system. Perfect for DIY enthusiasts or professionals, this full pack of 10 provides you with all the necessary elbows for your project.