3/8″ crushed limestone gravel (F rock, pea gravel) used for pipe bedding to level and support while allowing pipe to move slightly without losing position.
1″ crushed limestone gravel (#57 rock) used for pipe bedding and concrete aggregate. 1″ pipe bedding insulates pipe from soil movement caused by natural wetting and drying of the earth, traffic from above and other soil distress.
3/4″ – 1 3/4″ crushed limestone gravel (#63, #66 rock) used for railroad ballast and retaining wall drainage gravel. Also commonly used for landscaping and gravel road surfaces.