Seal Lock corrosion resistant self-locking collar nuts from Bollhoff avoid the need for separate washers, packing, or coated seating surfaces. They are a one-piece, re-usable high performance fastener which seals against gas or fluid pressures up to 450bar, even after the joint has been disassembled and re-tightening up to five times. Initial assembly torque and operating performance are maintained throughout a temperature range of -40° to +110°C.