... refers to derivative structure, its no. is indicated with H1, H2,H3...(for each frame no, arranged as per the sequence ... ZYT indicate PM DC motor.4. 90 indicate motor frame no. Frame no. is indicated with 55 ,70,90,110,130, ... 55,70,90,110,130mm. Mounting modelmounting modelmounting model no.frame no.single shaft extensiondouble shaft extensionhousing mountingA5AA555-130flange mountingA3AA355-130foot ...