Looking for a custom crib mattress? We start with a 4.5″ natural rubber core and cover it in our untreated, natural wool moisture resistant fabric. This natural wool outer will help to repel liquids, keeping the natural rubber core in good shape. Because wool is a natural fire-retardant, we do not use any fire-retardant chemicals in or on the mattress nor do we use a vinyl covering. We can make any size up to 28 x 52 x 4.5 and slightly larger. Please contact us for a quote if you need a size significantly larger than these dimensions. We also make custom size fitted crib sheets.