[en] We describe 10 strong lensing galaxy clusters of redshift 0.26 ≤ z ≤ 0.56 that were found in the Sloan Digital Sky Survey. We present measurements of richness (N₂₀₀), mass (M₂₀₀), and velocity dispersion for the clusters. We find that in order to use the mass-richness relation from Johnston et al., which was established at mean redshift of 0.25, it is necessary to scale measured richness values up by 1.47. Using this scaling, we find richness values for these clusters to be in the range of 22 ≤ N₂₀₀ ≤ 317 and mass values to be in the range of 1 × 10¹⁴ h ^–1 M_☉ ≤ M₂₀₀ ≤ 30 × 10¹⁴ h ^–1 M_☉. We also present measurements of Einstein radius, mass, and velocity dispersion for the lensing systems. The Einstein radii (θ_E) are all relatively small, with 5.''4 ≤ θ_E ≤ 13''. Finally, we consider if there is evidence that our clusters are more concentrated than ΛCDM would predict. We find that six of our clusters do not show evidence of overconcentration, while four of our clusters do. We note a correlation between overconcentration and mass, as the four clusters showing evidence of overconcentration are all lower-mass clusters. For the four lowest mass clusters the average value of the concentration parameter c₂₀₀ is 11.6, while for the six higher-mass clusters the average value of c₂₀₀ is 4.4. ΛCDM would place c₂₀₀ between 3.4 and 5.7.