Searching for more detailed mechanical information regarding ATS-EXL108-300-R0. Datasheet does not list values for mass (or mass/unit length).
I’ve not found mass figures quoted either, but there’s a 3D model available from the manufacturer’s product page at ATS-EXL108-300-R0 300.0 x 240.0 x 55.0 mm Extrusion Profiles (lengths) Profiles. If you’ve got a CAD package that’ll open that and calculate volume, a density figure of ~2.7g/cc should get a person quite close in less time than required to play a game of Telephone with the manufacturer.