If you're looking to build up a set of race wheels for your mini or junior race bike, then take a hard look at the Alienation BMX Mite TCS Rim. This brand has been producing the goods for race bikes of all sizes for many years now and are the go-to brand for aftermarket  alloy wheel builds in the sub-expert, and pro size custom bike builds. With 6069 T6 aluminium formed to produce double walled rims, these will be a perfect upgrade for any wheelset that you are looking at slotting into the dropouts of a entry level race bike, or as part of a custom build.

Though they are termed 20 x 1-1/8 rims, you can run both 20 x 1-1/8 or 20 x 1-3/8 tyres on them.