Example of (U, V, W) distribution of the member stars (blue) of the clusters NGC 6633, NGC 6281, and NGC 1662. Stars included in the spectroscopic analysis in this work are the orange crosses, and the stars discarded by discrepant kinematics are marked with green diamonds. The sample of member stars are those in Cantat-Gaudin et al. (2018) with membership probability > 0.7 and radial velocity determination in Gaia DR2. Not all plots are to the same scale.