The top plate is heavy aluminum while the nipple and center tube are steel and the drain appears to be stainless steel. Keep in mind this type of filter is best used to keep moisture out of your tools, not paint equipment. If I was painting anything critical I would use either an in line or a disposable desiccant filter. That's not to say that these aren't good, but that they aren't as efficient at removing contaminates like oil or silicone (which can destroy a paint job). But for what they are intended and how little they cost they're great. Two things I would say, make sure to use a wrench when attaching the filter to a tool or attaching anything to the filter (If you tighten it by hand it will be much more likely to leak over time). It doesn't come with installation instructions so make sure to attach the colored end to the tool with the air flowing from the nipple to the colored end. That will leave the actual seperator in the upper part of the housing and the drain at the bottom.