Boots for Mont Blanc are very specific in that they must have rigid soles to give support for several hours of crampon work and be sufficiently insulated to deal with sub-zero temperatures. A typical example is shown below:
La Sportiva Nepal Evo is the choice of many of our guides.
Great for Mont Blanc, but too stiff for general trekking.
If you tried to bend this sole with your hands you would barely move it a millimetre, and though this is not ideal for general trekking it really comes into its own when wearing crampons. This is a “B3” boot on the B1-B2-B3 scale you sometimes hear talked about in climbing shops, and if you bring your own boots they will need to be B3 standard (B2 boots are more flexible and less well insulated and are designed for short term crampon usage at lower altitudes; you can sometimes get away with them on Mont Blanc if it's particularly warm but B3 fit crampons better and are always warm enough).
If you have boots you’re not sure about either bring them with you anyway or send us a photo and we’ll let you know if they are good enough. Most of the people who develop blisters on our courses do so in boots they bought specially for the trip; if in doubt it's definitely better to rent from us, we have taken a lot of trouble over our selection of hire boots and we’re happy to give you all the help you need getting the right pair on the first morning when we’re checking equipment.They can also be changed mid-week of course if you’re not happy with them and would like to try a different size or model.
A good trekking boot, but not stiff or warm enough for Mont Blanc