These ingenious adjustable railing planters that fit on wood, composite or metal railings up to 4" wide, they even fit on chain link fence! - 24in L x 8in W x 7.5in H - Grey. Water reservoir holds 6 cups of water with auto-overflow; hidden tray separates plants from reservoir; with slits to allow only the roots to reach the water reservoir below; avoiding root rot. Excess water drains out the lower leveling support foot channel, no drilling is required.