Is this orthosis suitable for both hands, and how should it be put on correctly? — Wrist support with thumb holder (for left and right hand size 1 553L-1

Yes: the name of model 553L-1 states «for the left and right hand», size 1 (the English description of the card says the same). According to the card, the orthosis is put on directly on the body; the adjustable Velcro fastener in the thumb area helps adjust the fit and, if necessary, give the hand a suitable position, and the removable aluminium plate allows the rigidity of the fixation to be adjusted. The card does not state the size range in centimetres.

General information (not a manufacturer's instruction): the orthosis should hold but not constrict — if the fingers become numb, tingle, turn pale or blue, loosen the fasteners and take it off if necessary; in case of severe pain, swelling or a fresh injury, consult a specialist.