Save space and maximize vertical storage with the 7Penn Stacking Water Bottle Organizer Racks. Stack both 2 level water bottle storage racks by interlocking handles to create a 4-tier tumbler storage organizer on your countertop, under cabinet, or in pantry. Each shelf has a 16 bottle load capacity of 40lbs (18kg) and comes with 12 moveable rails for 750ml bottles up to 3.1in (7.87cm) diameter. Lock dividers into pre-drilled holes for 16 tumblers, shaker bottles, and insulated flasks, or rotate to use as front rails that hold 8 wine bottle necks (2 per tier). Lower shelf holds bottles up to 4.7in in diameter, while upper shelf of lower unit can house tumblers 3.9in (9.9cm) wide. Easily assemble with included hardware. Intended for water bottles only, optionally used with wine bottles. Warning: This product can expose you to chemicals which is [are] known to the State of California to cause cancer and birth defects or other reproductive harm.