The present invention relates to burst port subs (BPS) 120 allowing for a tubing 100 or a liner 200 or a casing 200 in a borehole 300 to be opened at a predetermined pressure and further providing a delayed opening sequence due to a dissolvable barrier 400, 500 arranged in a port 440, 540 of the sub 120. The present invention relates further to a downhole system comprising a predetermined number of such burst port subs (BPS) 120.