Manufactured from heavy duty PYREX® borosilicate glass for chemical and thermal resistance. Square bottles are easier to handle, require less space (13-20%) on the shelf or in the autoclave and are ideal for mixing, sampling and storage. Features include white enamel graduations, large marking spot and a glass ridge molded into the bottle to indicate full capacity. They include a linerless, one-piece autoclavable orange polypropylene plug seal cap and a drip-free pouring ring. Caution: Square bottles should NOT be used with bottle top filter units, or in other applications involving vacuum pressure, as breakage may occur. DO NOT tighten caps immediately after autoclaving as the vacuum resulting from cooling can cause breakage. See B5430 for optional caps.