Fantastic addition to a winter pack where patches of ice might be encountered and an extra bite is needed, but the bulk of a full boot and crampon combination are unnecessary or desirable.
Having used a pair extensively in Iceland on hard ice, with a pair of Goretex trainers, I was genuinely impressed and even found them stable and comfortable to run in. In snowier conditions they do have a tendency to ball up which is worth keeping an eye on, but I have used them through snowy, wintery days on the shallow hills of the Brecon Beacons and they served me well.
Sizing can be found in the table underneath. Sizing depends whether you are fitting to a shoe or a large boot.