Boot Rating
B0 - These are your traditional walking boots. They have flexible soles and uppers, consequently they take very little time to break in and are perfect for 3 season use below snowlines.
Despite the advances of technology, even with flexible linking bars, crampons are unable to flex as much as a B0 boot. The result of putting a crampon on a B0 boot would be the binding between crampon and boot being compromised, resulting in the crampon pulling loose, this potentially could be hazardous.
Crampon straps can dig into the upper of B0 boots that may lead to discomfort for the user; moreover the cradles and bindings of crampons could puncture soft uppers leading to the failure of a boots waterproofing. As a result for due to safety considerations, B0 boots are not recommended to be used with crampons.
B1 - These are considered to be a all round 4 season walking boots, they are stiffly constructed for long mountain days, scrambles and winter hill walking. They have a rigid midsole while the uppers are constructed from leather or fabric, it is common to find a rubber rand surrounding the upper to improve durability.
These are only compatible with C1 Strap on crampons and the combination would be more than adequate for winter fell walking.
B2 - Suitable for the summer alpinist and for the Scottish winter climber. These boots have both stiff midsoles and uppers, moreover there is just enough flexibility for general walking. The thicker uppers mean that these are slightly warmer than their B1 counterparts and models tend to have a degree of insulation.
B2s have a heel ledge to allow the fit of a C2 crampon allowing for a secure fit and all round versatility.
B3 - The best of the best, designed for full on mountaineering, year round alpinism, mixed and ice climbing. B3s have the stiffest soles and uppers available, allowing for unparamounted support on lateral and medial axis ideal for all aspects of mountaineering.
The category is split between both technical climbing models and high altitude double boots. Heel and toe ledges allow for the fitting of C3 crampons although it is not uncommon for them to be paired with a lighter C2.