An number of colourless fibre-reactive UV-absorbers, derivatives of monochlorotriazine were synthesised in which 2,5-diaminobenzenesulphonic acid was substituted by more popular and less expensive 2,4-diaminobenzenesulphonic acid ("RH-acid"). Application properties of new auxiliaries as well as Ultraviolet Protection Factor (UPF) of treated cotton tricot were determined.