This training ball is built to last with its synthetic cover and a special resilient filler material that retains its shape through year after year of hard use. Color coded for easy identification. 4 lb. ball (2 kg): 6" diameter; red & white. 6 lb. ball (3 kg): 7.8" diameter; yellow & white. 10 lb. ball (4 kg): 7.8" diameter; blue & white. 12 lb. ball (5 kg): 8" diameter; orange & white. 14 lb. ball (7 kg): 8.4" diameter; green & white.