What are they and what do I with them?
When I bought a DVD recorder I transfer my VCR tapes to DVDs. Some of my tapes inside the cassette were torn in two.That's where the VCR hubs come in because each hub had a clear leader (transparent plastic).
I splice the clear leader between the two halfs of the broken tape with electric tape. Why? Because a splice will ruin the videotape heads but the senor will stop the tape when it hits the clear leader and before it gets to the videoheads.
Once I transfer the first half of the tape I pause my DVD recorder; take out the tape and turn the hub to the second part ;place the tape back in the VCR and press play and unpause my DVD recorder and continue
Remember this is in the time when VCRs were expensive $200 on up.Good luck in finding VCRs these days.
The VCR video heads are on the head drum and each record/play head is about 1/2 size of a dime ;on 2 headed VCRs each head records 1/2 of a video signal diagonally.4 headed VCRs are use for special features such as frame by frame, double speed etc.
When I am finish transfering my VCR tapes to DVD I open the cassette and throw away all the tape and just keep the hubs with the clear leaders.
I had three cabinets that were filled with VCR tapes now since they were transfered to DVDs they all fit on one shelf.
Always store CDs,VCR tapes, DVDs vertically in a cool place.