The typical KF or NW assemblely consists of two identical flanges, a centering ring, and a clamp with wing nut fastener frequently connect and disconnect withou tools. 

The vacuum seal is effected by uniform appication of pressure by the clamp on surface of the flange.

The mating flange surface compress an Oring (held in place by centering ring) to generate seal.

The components of ISO universal flange system are defined by the international standards organiation.

The construction of ISO flange series includs two smooth-faced flanges clamped together with a combination etal centring ring and elastomeric O-ring between them. 

ISO components are reusable and changeable with other ISO dimension components of the same size.

The high sealing effect and the low leak rates performance of CF flange connections is a result of gasket material. When assembling the CF flange connects, the knife edge is pressed into the flat copper gasket and force the seal material both axially as well as radially outwards to the flange. The matrial is enclosed and cannot flow even at high bake termperature. Due to this deformation of the seal such connections may sometimes stick together. They can be easily separated with a special tool or screwdriver.