The drums you need for this HPA ADAPTER are sold separately, they are available here

We will fit the drum for you if purchased with this adapter.

This represents the culmination of months of work to produce, from scratch, a shortened magazine for the KWA VZ61. This leads to an ultra lightweight magazine setup, that is both more enjoyable and economical than buying the gas mags. Aesthetically I feel this setup is far greater than those which attach to the bottom of the 20 round gas mags.

A donor mag is required for feed lips, exhaust valve and gas route. The installation is largely the same as our TM MP7 HPA Drum for which the tutorial is here (https://www.youtube.com/watch?v=vwScbjK5r7I&ab_channel=AirtacJames)