The design with two spiral-shaped mixing spirals creates a mixing effect from bottom to top. This allows it to work its way effectively into denser materials and to pull itself down to the bottom of the bucket. As a result, it efficiently promotes heavier material components, such as sand aggregates, upwards. It is particularly suitable for heavier, end-moist materials. The closed protective ring on the mixing basket prevents damage to the mixing bucket and ensures smooth operation of the mixer.