Caution: These square polycarbonate 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. Strong polycarbonate bottles are more break resistant than other glass or plastic bottles. Use a linerless, 45mm one-piece autoclavable orange GL45 threaded polypropylene plug seal cap. Screened white enamel graduations are easier to see than molded graduations Sterilized by gamma radiation Large white marking spot for easier identification Bottles can be autoclaved once at 121ºC and 15psi. Repeated autoclaving weakens polycarbonate and is not recommended. Optional reusable caps with silicone septa (Corning Cat. Nos. 1395-45HTSC, 1395-45SS, 1395-45TS) for syringe sampling or introduction of reagents are available for these caps. Note: Most GL45 threaded caps designed for glass storage bottles use a different sealing design and will not give a secure seal if used on these plastic bottles unless they have a rubber liner.