Manyleb a model gwregys aml-letem

PH, PJ, PK, PL, PM

Ystyr gwregys aml-letem

Er enghraifft:

1) metrig: 10pj1089

Rhif lletem (rhif brig): 10

Hyd effeithiol (adran): 1089mm

2) system Saesneg: 10pj250

Rhif lletem (rhif brig): 10

Hyd effeithiol (perimedr rhan): 25 25.4=635mm