So at this point by me a tip on how you calculate the correct Unicycle greatness:
1) First, to measure the driver's stride length (= the distance between the ground and step), preferably with appropriate street shoes on (so you sit then also on a unicycle)
2) A detailed look at a novice still 2cm from (it's easier to learn to ride)
3) Now apply the following standard values for the unicycle:
12 inches = minimum inseam 48cm
16 inches = minimum inseam 55cm
18 inches = minimum inseam 58cm
20 inches = minimum step length 61cm
24 inches = minimum inseam 68cm
26 inches = minimum inseam 74cm
36 inches = minimum inseam 84cm
We bought our daughter two years ago this unicycle, and are absolutely delighted.
It is very suitable for beginners and can be adapted from the saddle height flexible to the child's growth.
And above all: It is really extremely robust, has survived many a fall without prejudice and drives and drives.
Depending on athleticism and sense of balance of the child, in my opinion is an apprenticeship of unicycling at the earliest with 6-7 years useful. While even young children can learn to ride a unicycle, but then they need very much endurance and also a really good coordination skills (Unicycling is not as easy as it looks, if only the upgrade requires some balance ...).
My daughter loves it, at all events, to operate on their unicycle, she learned it very quickly and now combines fun with great sportsmanship and a lot of coordination.
I can therefore absolutely recommend the purchase of such a unicycle, but you should have a way where the child can practice regularly and go.