In reply to Cardi:
This list is taken from the TGR Forum...
THE LIST (stiffest ---> softest) as of March 10, 2013
-------------------------------------------------------------------
130 - Dynafit Vulcan, Tecnica Cochise Pro 130
120 - Scarpa Mobe, Tecnica Cochise Pro 120
115 - K2 Pinnacle 130
110- Dynafit Mercury
105 - Scarpa Maestrale RS, Dynafit Zzero ("Green Machine") CF 4-buckle [2011-12 version with full carbon cuff)
100 - Dynafit TLT6, Tecnica Cochise Light 120, Black Diamond Factor, Dynafit Titan, Titan UL, Scarpa Hurricane
95 - Scarpa Typhoon/Skookum (stiff tongue), Garmont Endorphin, Garmont Axon
90 - Dynafit TLT5 Performance, Dynafit One PX, Black Diamond Quadrant, BD Prime, Garmont Radium, Dynafit ZZeus, Dynafit Aero Freeride (4-buckle)
85 - Scarpa Maestrale, Scarpa Tornado/Pro (black tongue), Dynafit TLT5 Mountain, Scarpa Spirit 4 (black stiffer tongue), Garmont Adrenaline, Dynafit Zzero ("Green Machine") CF 4-buckle [pre 2011-12 version), Black Diamond Method, Salomon Ellipse e2
80 - Scarpa Denali XT/TT, Scarpa Spirit 4 (green softer tongue), Lowa Struktura Rodeo/Pro, Dynafit Zzero PX 4-buckle
75 - Scarpa Rush, Scarpa Spirit 3, Garmont Megaride/G-Ride, Lowa Struktura Evo, Dynafit Aero Speed (3-buckle), Dynafit Zzero CF 3-buckle
70 - Scarpa Matrix, , Old Scarpa Denali (4-buckle red shell), Dynafit TLT 700
60 - Scarpa Laser, Garmont Dynamite, Dynafit TLT 500 (2-buckle + strap), Scarpa F3
50 - Scarpa F1, Garmont Megalite, Dynafit TLT 4 Evo (3-buckle), Dynafit TLT 4 Lite (2-buckle + strap), Dynafit Zzero 2C
40 - Scarpa F1 Race (2-buckle, no strap), Dynafit TLT Race Pro (1-buckle + strap)
Although ski boot flex/stiffness ratings assigned by manufacturers are not very precise, if you know the flex/stiffness rating of alpine boots you have previously skied in, then the above list might give you an idea of which AT boots will suit you.