The Apple USB Type-C Cable is retailing for S$42 and comes in only one length which is 2m. I wish they have it in 0.5m and 1m as well.
There are no markings on the USB ends on the cable because there is no need to since it has a reversible plug orientation. This is similar to the Apple Lighting cable as there is no marking on the Lightning end of that cable as well.
My family got me the Apple Thunderbolt Cable (2m) from Apple Store at IFC, Hong Kong when they are there for a holiday. It is retailing for HK$288 in Hong Kong and S$48 in Singapore. Due to the weakening Singapore Dollar against the Hong Kong Dollar, it is about the same price after currency conversion. It used to be slightly cheaper.
You can connect your MacBook Air to your iMac using this cable and this will turn your iMac into a secondary monitor.