This small 9:1 UnUn was made to team up with an SDR receiver such as the SDRPlay RSP range to provide a simple and lightweight impedance matching network for an end fed long wire antenna. I use one myself for holidays and weekends away and it works great.
It’s wound with 25 SWG (0.5mm) enamelled wire on a Micrometals Iron Powder Toroid T80-2 core so could also be used for QRP transmit. I’ve not tested this but should be OK for 5W or under.
The genuine Hammond enclosure measures 35mm wide (excluding binding posts) x 76mm high (including mounting lugs) x 20mm deep and comes with 2 x binding posts that can also accept a standard 4mm banana plug and an SMA Female connector.