Warrior DAR chest rig - info needed

[Rimms]

Ive just got a DAR chest rig second hand and I would like to know if its meant to have something to pull it tight round the back
Every chest rig ive used has a strap on the back to pull it tight as well as the two shoulder straps but the warrior rig only has the two shoulder straps and as much as I tighten the shoulders its still feels lose
There are 4 clips on the rig, 2 for shoulder straps so I'm wondering if there is meant to be a strap that clips in to the other 2 and he's not sent me it

If its does not come with one can you buy something as it really needs something to pull it tight