they have slots in the sides, floor, and ceiling of each locker... but 1 active unit like the hydra lg that is recommended for it cant really push the RH properly (IMO) through all of that space and those barriers.. RH in the bottom lockers was always a bit high (70-72)... and at the top was always a bit low (60-62ish)...
My solution was pretty simple.. I just threw my own seasoned desktop in there along with a couple of 65 RH bovedas.. and I stayed a rock solid 65 all the time.. and the bovedas never seemed to dry out (between the active unit always pushing RH from below.. and the sealed desktop sitting inside a sealed locker.. there was very little air transfer other than when I went in there once every couple of weeks to grab a stick or two out..