Wingtra High Altitude Propellers for WingtraOne Drone, Pair

As air becomes thinner at higher altitudes, the ability for standard propellers to generate enough thrust to lift an aircraft is compromised. Their shape must change to lift through these conditions.

For flights above 2500m AMSL, these are required, plus they increase flight duration and safety for flights above 1500m AMSL

With the normal propellers, you can take off up to 2500 m (8200 ft) AMSL. For flying higher, you need the high-altitude propellers, which allow taking off at altitudes up to 4800 m (15.700 ft) AMSL and flying at altitudes up to 5000 m (16400 ft) AMSL.

Note:
High-altitude propellers can only be used from a home location above 1500 m. Normal propellers can only be used from a home location below 2500 m. Between 1500 m and 2500 m, both types of propellers can be used. However, your flight time will be substantially higher with the high-altitude propellers.

Taking off with normal propellers above 2500 m AMSL is not possible.