Flist ring nuts made of AISI 316L (X2CrNiMo17-12-21.4404 UNI EN 10088-1) stainless steel. Produced from a hexagonal bar they have a reduced thickness. That allow threaded connectors to be coupled to other equipment (boxes, cabinets, ducting) that have no threaded holes. The thread is ISO metric in compliance with CEI EN 60423.