The better_grass.7z file you have requested: Clear Sky / Mods / Singleplayer / Better Grass - 60.18mb is not available. Perhaps try browsing all files for the game S.T.A.L.K.E.R.: Clear Sky and upload any files you want to share or are missing. This is the only information we could locate:
This mod adds higher and better grass to all levels(only Limansk not). Because of its size, good pc-lineup is required. Otherwise, you can receive a bug.