What flow rate does it deliver in liters per minute?

The listing does not state a continuous flow rate in LPM. The 8L in the name is not explained, and the 4LBS figure refers to weight, not output. Ask the seller for a spec sheet before relying on it.

Is the 90% oxygen purity measured at the full flow?

Purity claims only mean something at a stated flow rate. No flow is given here, so the 90% figure cannot be checked. Clinical concentrators publish purity at each setting.

Does it run on battery, and for how long?

No battery capacity or runtime is listed. Travel concentrators usually quote hours per battery and whether they can run on AC, DC car power or both. Confirm this before a trip.

Is it FDA cleared for medical use?

The listing shows no clearance number. In the US, oxygen concentrators are prescription devices and need FDA clearance. Without it, treat this as a non-medical air device.

How does it compare with an Inogen or Philips portable concentrator?

Those brands publish flow settings, purity at each setting, battery hours, weight and noise in decibels, and have repair networks. This unit publishes none of that, so the comparison cannot be made on features.

What comes in the box?

The listing does not itemize the package. Check for cannula, AC adapter, car cable, battery and filters before buying, since generic units often ship with few accessories.