LONGER THREAD The NPT cable glands Kit are designed with 15mm(0.6") long thread. It's much longer compared to others. More importantly, the cord grips are suitable to install on thicker electrical boxes or other place. MULTIPLE SPECIFICATIONS There are five types of power cord grips to apply in different scenarios. Total 72 pieces, including 20pcs PG7(3-6.5mm), 20pcs NPT 1/4" PG9(4-8mm), 20pcs NPT 1/2" PG13.5(6-12mm), 8pcs NPT 3/4" PG21(12-18mm) and 4pcs NPT 1" PG29(18-25mm).