X Series  (current range replacement):

X-D     (X-R low-sens capsules)
X-M    (X-R measurement capsule)
X-O    (X-R omnidirectional capsule)
X-Q    (X-R omnidirectional capsule)
X-S     (X-X microphone)
X-T    (X-R omnidirectional capsule with transformer output)
X-T/D    (X-R lows-sens capsule with transformer output)
X-W    (X-R omnidirectional capsule with EQ disc)

U Series:

Most U Series products can be converted to the X-R system; please inquire.

amplifiers
capsules

MSH Series  (current range replacement):

MSH-1 (all variants)  (X-R omnidirectional capsule)
MSH-2 & MSH-2T  (X-R omnidirectional capsule)
MSH-3   (X-R low-sens capsules)
MSH-4  (X-V tube microphone kit)
MSH-5

box series:

Most input formats can be supported by the IPA inline amplifier.

littlebox & midbox
PIPsqueak
tinybox
tinyhead

Inline Devices:

ITP inline amplifier  — (see IFA or IPA for replacement)