A chain case is a great idea for utility bikes – it weatherproofs your chain and keeps oil off your trousers. The Hebie Chainglider is a clip-together plastic sleeve for singlespeed or hub gear chains. It rests on top of your chain rather than attaching to your frame, which adds a bit of friction but means you don't need tools to fit it.
The Chainglider weighs 225g and comes in three sizes, to fit a 42-44 tooth chainring and 19-20 tooth sprocket, a 38 tooth chainring and 18-22 tooth sprocket or a 42-44 tooth chainring and 15-17 tooth Rohloff sprocket. For any of these, the bottom bracket to rear axle distance must be 44-48cm.
The clip-on case worked fine on a three-speed Dutch town bike, except that the gear cable’s eyebolt fouled the Chainglider in first gear. It would work better alongside a hub gear with a covered cable all the way to the hub.