Sure, you can hang your Koshi outside but please be aware that it is a wodden object.
The bamboo tube and the wooden plate have been slightly oiled to give your Koshi protection.
Please treat your Koshis regularly with a protective oil, linseed oil for example. We also recommend to hang your Koshis where they are protected from rain (underneath an overhang) .
You can also get creative.
If you like it more colorful you can use some lacquer on your Koshis or paint them.
