This performance gain has been achieved through the use of special plastics featuring higher values of CTI (comparative tracking index: a measure of insulation capability defined by Underwriters Laboratories). These new plastics comply with the Group II specification, with a CTI of between 400 and 600, while the standard plastics are classified as Group IIIa or IIIb, with a CTI of between 100 and 400. Given a creepage distance of 1.2 mm, the voltage between two adjacent contacts can amount to 160 V: considerably higher than the usual 50 V.
The new connectors are available in types C, 2C, 3C, B, 2B, 3B, R, 2R and F. Additional construction types and sizes are available on request.