Back when the VHS format reigned supreme, it actually had two different sizes. There was the standard VHS tape that everyone knows and there was also the VHS-C. VHS-C tapes are basically compact versions of the VHS tape, made smaller to fit the much more desirable handheld camcorders. The creators of this tape felt they had a great idea, but needed a way for people to easily play these tapes on their existing home equipment. This is where the VHS-C adapter comes in. This VHS-C adapter will hold your VHS-C tape, and mount it in a shell of the same size and shape of a VHS tape, allowing it to play in your home VCR with no additional modifications.
If you have Maxell VHS-C tapes, this third option might be the best for you. The reviews seem to indicate that it may have problems getting stuck in some models of VCRs. This adapter is probably adequate for simple jobs such as VHS-C to DVD transfers or simple viewing on your TV.