In Cu 380A, 380 represents
Number of turns of copper wire
Surface area of CuT in sq.mm
Surface area of Cu in sq.mm
Effective life of CuT in quaers
The numbers included in the names of the devices refer to the surface area (in sq.mm) of the copper on the device. Metallic copper has a strong anti-feility effect.Park 23e pg: 496
Demography and family planning