G&G One piece outer barrel TR16

[jim1h]

Does anyone know if I need a specific G&G tool (armorers wrench) to tighten the barrel (slight up and down movement) or can I buy the ones they sell on ebay sort of a multi wrench? the AEG is a G&G Top tech tr16 A3.

There are no grub screws near the delta ring I thing the barrel just locks into the top receiver but cant see any way to tighten it.