Integrated weight pouches were originally held in place with velcro and were notoriously unreliable. At the end of a dive on the Thistlegorm in the Red Sea many a weight pouch would rain down the shotline on ascents and descents providing an extra hazard for the divers on the line!
Then Seaquest came along and invented the SureLock system- a weight pouch that connected with a reassuring click but that could still be released with a single hard pull. Seaquest was bought by Aqualung and now the SureLock pouch features in all Aqualung and Apeks BCDs. However there are various versions of the weight pouch and it can be quite confusing to know which one to purchase if you lose one!
First off there is a SureLock and a SureLock 2 system. There is a slight cosmetic difference between the pull handles of the 2 systems but the only real difference is that the SureLock 2 has rails on the back of the pouch to help guide it into place on the newer BCD styles. However, both Surelock 1 and 2 pockets will fit into both old and new BCDs.
The main thing to check is that you are purchasing the right size pocket for your BCD:
Aqualung SureLock II single weight pocket 10lb/4.5kg (BC911143)
This is the standard 10lb weight pouch that works with pretty much all Aqualung and Apeks BCDs. It also works with any Seaquest BCD with the SureLock system including the Pro QD and Diva LX. It will also fit into the WTX weight pocket system for the Apeks tec range.
It is not the same as the weight pockets that come with the Apeks Black Ice but it will still fit (albeit with a fair bit of room to spare). It is also smaller than the weight pockets that come with the Aqualung Axiom or Pro HD in size L or above but again will fit without a problem.
Aqualung SureLock II single weight pocket 16lb/7.3kg (BC911144)
This is the dual channel pocket that fits the Apeks Black Ice BCD and also the old Seaquest Pro QD in size L and above.
Aqualung Outlaw SureLock II Weight System (BC116113)
This system incorporates the modlock attachment which fits to the back of the Aqualung Outlaw or Rogue BCD. This version incorporates the weight pocket holders and the weight pockets themselves which are the standard 10lb weight pocket (BC911143).
WTX Surelock system (BT115116)
This system incorporates the weight pocket holders and the weight pockets and utilises the attachment plates to fit to the Apeks WTX harness range. Again the system still takes the standard 10lb pouches (BC911143).