Bronica ETR ETRS question

I got a 220 back from eBay, and my spare 120 insert works A-OK.
I'm surprised and pleased by the number of responses on this thread. Thanks everyone for all the information.

There is a lot of misinformation, nonsense, and pure BS about using 120 film in an Bronica ETR 220 film back. I have used 220 backs with 120 film for years. I load them same as with 120 backs. I have no problems with the pressure plate at all. The film winds smoothly just like in a 120 back. I get 15 exposures on a roll of 120 film. After the 15th exposure, I simply wind the film onto the take-up spool manually. ...Nothing to it. And the best part is that 220 backs usually go for about half the price of 120 backs! I use one 120 back and three 220 backs. And interchange them frequently mid-roll with no problems. I love my ETRSi!

The backs consist of a shell and an insert.
The insert has all the mechanisms for counting and metering frames. It is labeled as either 120 or 220 on the side that has the darkslide slot.

The shell just holds the insert and stays on the camera with the darkslide when you open the door to access the insert. With the darkslide in place you have the option to remove the entire back, the darkslide has a tab on the bottom edge of the handle that will release the interlock so this is possible.

You can swap 120 n 220 inserts into any of the shells.
Newer backs are backward compatible.

To use 120 in a 220 back, you will have to start the winding not at the arrow, but at the very beginning of the paper leader in order to get frame 1 properly aligned. Also once you reach the 15th frame, you will have to advance your film frame by frame till you advance enough of the backer paper to be sure its entirely off loaded from the spool.

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That settles that.