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. 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.