How to check SQL Server Filegroup file sizes

I had a question from a fellow DBA about how to list every file  per SQL Server filegroup , and report on the size in MB. This will give them a quick way of checking which file could be creating a capacity issue. 

Quite often , alerting is set up to check the whole drive , but won't check every file. So some granular report can identify the file causing a capacity issue 

--Return file , size in MB , filegroup 

SELECT sdf.name AS [File_Name],
sdf.size/128 AS [Size_MB],
fg.name AS [FileGroup_Name],
sdf.physical_name as [File_physical_name]
FROM sys.database_files sdf
INNER JOIN
sys.filegroups fg
ON sdf.data_space_id=fg.data_space_id

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