Slimline hot water radiant baseboard heating panels are aluminum extrusions with 3/8" copper pipe running through them. The copper pipe protrudes 3" on each end, which allows the use of either copper or PEX Pipe for the panel connections. The Slimline comes with a durable white finish that is guaranteed not to rust. If different colors are preferred, the panels can easily be painted after installation with an oil-based enamel.