Basic reference for vacuum flange standards:
CF (Conflat) Euro/Asian size = N.A. size (inches, dia.)
KF/QF Klein Flange (KF) or NW, also DN
ISO ISO flanges are known as LF, LFB or sometimes just ISO flange. ISO-K (or ISO LF) flanges are joined with double claw. The ISO-F (or ISO LFB) flanges have holes for attaching the two flanges with bolts.
ASA Flange sizes are indicated by tube nominal ID, or by flange OD (in inches):