These are one-touch connection connectors that allow you to connect cables simply by inserting the stripped cable 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 990 yen for two. I don't have a use for them, so I'm offering them at a super special price of 50 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 BNC male connectors also listed. If you purchase the items also listed at the same time, I will discount the shipping difference, so please let me know.