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Pumpable crib support for longwall gates and ventilation bleeder entries is becoming more prevalent in United States coal mines.The pumpable crib selection and spacing design has been greatly refined by the full scale testing conducted at the National Institute for Occupational Safety and Health (NIOSH) Mine Roof Simulator.The peak load on 24,27, 30 and 36 inch diameter J-Cribs is on average 300, 400, 450 and 650 kips, respectively.Standard J-Crib have a useful deformation of approximately 8 inches.The maximum useful deformation can be extended to 18 to 20 inches with exterior reinforcement layer or an interior double wall, for all four J-Crib diameters.J-Crib diameter is primarily a limited by a maximum 4.5∶1 height to diameter aspect ratio.Spacing is controlled by immediate roof stability, anticipated pillar deformation, and roof bolting practice.Approximately 500000 J-Cribs have been successfully placed in 18 different United States longwall coal mines.The selection and spacing of the J-Crib utilized to date is summarized for each mine.