For the stationary Oxygen concentrators you can choose from the following manufacturers:
Drive Devilbiss Healthcare: Compact 525 and the 1025
Kröber: Model 4.0
Philips Respironics: Everflo
Inogen: Inogen At Home
Caire Inc: Visionaire and Intensity
For the portable oxygen concentrators these are:
Drive Devilbiss Healthcare: IGO and the IGO2
Philips Respironics: SimplyGo and the SimlyGo mini
Inogen: Inogen One G3, Inogen One G4 and the Inogen One G5
GCE Healtcare: Zen-O and the Zen-O Lite
Caire Inc: Sequal Eclipse 5 and the Freestyle Comfort