Airsoftjunkiez demo one of the more recent custom HPA builds. You can check their custom build section to check even more HPA-powered airsoft guns using some of the most sought after HPA engines in the market... "Airsoftjunkiez custom HK416 with Wolverine Reaper and PolarStar UGS stock. 1.2J with .28g HPA BBs."

The PolarStar  Airsoft UGS CO2 Inserts and accessories to go with the UGS are available right now at Airsoftjunkiez... "Polarstar CO2 inserts are manufactured for both the UGS and CGS stocks and have models for both the 12g and 33g CO2 cartridges in either variant. However, the inserts have more uses than just being paired with one of these stocks.

PolarStar Airsoft posted on their Facebook Page, the CO2 Insert for the PolarStar UGS which will be released in late July... "Introducing the CO2 Insert for the UGS. These inserts allow you to reconfigure your UGS stock from running the standard 13/3000 HPA tank to a low profile, Mil-Spec buffer tube sized cylinder so you can use Mil-Spec AR buttstocks. These were developed in parallel with the upcoming CGS and has two variants for the 12g and 33g CO2 cartridge.

101 Tech, a U.S. distributor for various airsoft brands, announce that they are now carrying the Universal Gas Stock (UGS) from PolarStar Airsoft... "With the PolarStar UGS™ (Universal Gas Stock) you can now get the performance advantage of a HPA system without needing to be tethered to a remote air rig and still retain the likeness and function of a traditional adjustable AR-15 stock.

Airsoftjunkiez are taking pre-orders for the UGS being produced by PolarStar Airsoft... "The Type 2 is designed for use with traditional TM Spec M4 series AEG receives. (Modification of the receiver and gearbox is required). With the PolarStar UGS™ (Universal Gas Stock) you can now get the performance advantage of a HPA system without needing to be tethered to a remote air rig and still retain the likeness and function of a traditional adjustable AR-15 stock.