That Midwest Industries Folding Picatinny Buttstock Interface looks very nice.
My recent order from Brownells was held by CBSA for 19 days (and not opened apparently as there is no tax/fee attached to the CP tracking still enroute from Mississauga).
It contains 1 x 1911 slide stop and a micrometer top for a reloading die.....
A Numrich order which has Mauser parts has been there for 18 days 'so far'.
Good luck with yours as they may decide it can fit on an AR and prohibit it from entering.