High quality professional alarm cable Product Description OC-138A 4*7*0.16TC OD3.2MM OC-138B 4*7*0.18TC OD3.4MM OC-138C 4*7*0.20TC OD3.6MM OC-138D 6*7*0.20TC OD4.1MM OC-138E 8*7*0.20TC OD4.5MM