This blue 4mm plug has a 4mm socket in the rear providing an in-line stacking facility. * Lead wire is clamped in position by a screw * Nickel plated brass insert with stainless steel plug spring * 30A rating https://elecena.pl/product/27167682/truconnect-blue-4mm-stackable-plug 2024-11-07 https://elecena.pl/product/27167682/truconnect-blue-4mm-stackable-plug 2026-05-14