The "KT4" is NOT the "Millennium TurboHead".
The KT4 is "Kit, TurboHead, No.4" featuring the Millennium TurboHead along with the MN15 & MN16 Lamp Assemblies.
The KT4 kit should not be used on the M4 or M6 bodies as the kit features the incorrect Lamp Assemblies.
Models featuring the Millennium TurboHead:
Handhelds:
M3T, M4 & M6
WeaponLights:
M5xxAB & M500B rifle & carbine forend WeaponLights
M9xxAB Vertical foregrip WeaponLights
M97 & M98 Series Millennium Universal WeaponLights
Millennium Series versions of the Leopard Light
KT4 and KM501 conversion kits
LU15 & LU20 Lamp Modules.
Models featuring the Millennium bezel (aka "M3" bezel or Z46):
Handhelds:
M3
WeaponLights:
M5xxA rifle & carbine forend WeaponLights
M9xxA Vertical foregrip WeaponLights
M96 Series Millennium Universal WeaponLights
M1xx Millennium Series Handgun WeaponLights
Z46
KM500 conversion kit
LU10 Lamp Module
The KL2 was designed for the M3, as was the KL6 (sold as the L6 on the M3 body with Z58 Clickie TailCap)
There was also the L6-PP Porcupine featuring a special edition body and KL6 bezel along with the SW02 TailCap.
The M1 doesn't have a removable bezel so it's the loner of the Millennium Series.
The M2 is an uprated C2 featuring the toughened "M2" shock isolated bezel. Since this bezel fits on standard body SureFires such as the 6P, G2 etc it isn't a true Millennium Series model in the same way the M3 is. In fact the Millennium Series could be said to centre around the M3 - it was the model that SureFire used to re-write the Lamp Assembly and reflector design handbook.
If I've missed an Millennium Series models out I'll update this post...
Al