spending most winters in the alps i have come across these before .these are an allternative to snow chains and so can only used on snow, once you hit a cleared road they need to come off.Also they will have a max speed probably about 50mph.dedicated snow tyres have amazing grip when the roads are wet or snowy but on cleared roads wear quickly and make lots of noise.winter tyres are a good compromise for our winters .these tyres will have a compound which stays softer at very low temps and a tread pattern which squeeses the snow when the weight of the car rolls over it.this months autoexpress has a winter tyre test.