Looks like a Manfrotto 577 Rapid Connect Adapter w/Sliding Mounting Plate right? It sure could be, but guess what - it's not Manfrotto. On sale right now this QR adapter sells for about 40% of the Manfrotto price. The specs over at the Calumet website doesn't state anything about being Manfrotto compatible or as a Manfrotto replacement part. I called the store and they weren't even sure if it was.
I don't know why they don't state it anywhere on the specs of the product, but it does look to be the exact same QR adapter and Plate design. The question I had was 'Is it really compatible?'. So I just put this quick release through the tests and it sure is compatible in every means. If you're looking for a QR adapter for all your Glidecam, Flycam, Sliders, or Jibs, it's a bonus that this inexpensive one is Manfrotto compatible. Right now it's on sale and there's only a limited supply in every store. If you were wondering too, here's the answer..
Quick Release Adapter + Plate (not Manfrotto branded)
If you're just in need of the plate itself, they have that available too (again not stating Manfrotto Compatible)
Sliding Plate (not Manfrotto branded)