The McAlpine BW1A 1¼" Chrome Plated Plastic Basin Waste is a type of basin waste fitting designed to be used with basins or sinks in bathrooms and kitchens. The "Backnut" refers to the nut at the back of the fitting that secures it to the basin or sink, while the "60mm Flange" refers to the diameter of the top part of the fitting that sits on top of the basin or sink. The "3½" Tail" refers to the length of the pipe that extends down from the flange and connects to the plumbing underneath the basin or sink. The basin waste fitting also comes with a plug that can be used to stop water from draining out of the basin or sink when needed. The plug can be operated using a lever or chain mechanism that is typically located on the top of the fitting. Overall, the McAlpine BW1A 1¼" Chrome Plated Plastic Basin Waste is a durable and reliable option for anyone looking for a basin waste fitting that is easy to install and use. ・ Available Slotted or Unslotted ・ Available with Black PVC of Chrome Plated Plastic Plug ・ 1¼" BSP ・ 60mm flange ・ 3½" Tail