for what year? Dimensions did change so now and then.
Demensions are described in some of the regulations as well
as Mitteilungsblatt der RZM.
This is from 1936 for enlisted ranks:
The HJ visored cap was described as an oval shaped Tellermütze (saucer-style), being 23.0 x 25.0 cm.
The cap was being fabriced from light-brown waterproof and unshrinkable trill.
The top in the front (with a size 54) is 5.0 cm high.
The size for the side panels is 4.5 cm. The crown had to be piped according the new system,
as authorized in late 1935, either in bright red felt (or silk) material, light-blue and pink. The
size for the pipings was officially 2.5 mm. The felt pipings are most often found to be thicker. -*-
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"Herstellungsvorschriften der Reichszeugmeisterei" (further referred as "HV.d.RZM") 1936, p.119;