These are one-touch connection connectors that allow you to connect cables simply by inserting the stripped wire while pressing the button. No soldering or tools are required, and they can be attached and detached repeatedly. They seem to be sold on Amazon and Mercari for around 700 yen for two. I don't have a use for them, so I'm offering them at a super special price of 60 yen each. The compatible wire gauge is up to AWG18 / 1.0mm / 0.75SQ. The cable insulation should be stripped 8mm to fit perfectly. The fourth image shows them combined with the RCA male connectors also on sale. If you purchase the items also on sale at the same time, I will discount the shipping difference, so please let me know.