Abstract: An anti-skid device (1) with mounting from the outside is described, comprising: a central hub (2) designed to be disposed to coincide with the wheel hub (101), a plurality of arms (20) protruding radially from the hub (2) and ending in terminal elements (21) designed to be disposed on the tyre tread, portions of chain (3) connected to the terminal elements (21) so as to form a ring on the tyre tread, an adapter device (5) adapted to be fixed to a wheel-fixing bolt (102) and carrying a tensioning strap (7) which passes through the hub (2) of the anti-skid device (1) to be tensioned by the user so as to move the hub (2) of the anti-skid device (1) towards the hub (101) of the wheel, a tensioning device (8) connected to the hub (2) of the anti-skid device (1), adapted to be operated by the user, to tension and to lock the tensioning strap (7).

Abstract: A non return block (5) for locking a tensioning terminal portion (7) of snow chains (2), comprising a body (51) which defines a channel (12) in which the terminal portion (7) passes and a ratchet or a pawl (13) pivoted on the body (51) to lock the terminal portion (7) is described. The non-return block comprises at least one insert (62, 63) of soft material fixed to the body (51) of the non-return block so as to protrude laterally therefrom to come into contact with the rim (8) of the wheel of the vehicle, avoiding deterioration thereof through rubbing.

Abstract: A non return block (5) for locking a tensioning terminal portion (7) of snow chains (2), comprising a body (51) which defines a channel (12) in which the terminal portion (7) passes and a ratchet or a pawl (13) pivoted on the body (51) to lock the terminal portion (7) is described. The non-return block comprises at least one insert (62, 63) of soft material fixed to the body (51) of the non-return block so as to protrude laterally therefrom to come into contact with the rim (8) of the wheel of the vehicle, avoiding deterioration thereof through rubbing.