a position stacked on top of a second bottom contain 1020 u2032 the top container lifts slightly as the rounded portion 1110 u2032 of the bottom container forces the rounded portion 1080 of the top container upward as best seen in fig2 there is a similar lateral nesting of the lateral edges of a top spacing feature with a bottom spacing feature top spacing feature 1110 and bottom spacing feature 1080 are provided with a thickness or vertical height such that stacking of container 1020 on top of container 1020 u2032 results in a gap 1130 formed between bottom 1050 of the top container and top 1090 u2032 of the bottom container as best seen in fig2 and 25 the relative spacing of spacing features 1080 and 1110 preferably provides a continuous gap 1130 between the sidewalls of base midsection 1040 this gap 1130 preferably extends from one sidewall 1054 to another sidewall 1052 as best seen in fig2 thus allowing circulation of sterilant vapor from central portions 1056 and 1100 u2032 to the outside of the stacked containers in the embodiment shown in fig2 planar surface 1084 u2032 is spaced apart and spaced below the underside surface of bottom 1050 u2032 in addition the top surface of planar portion 1114 is spaced apart from and spaced above the top surface of top 1090 further container support surface 1075 is spaced apart from and spaced below the underside surface of channel 1060 u2032 as best seen in fig2 the weight of a container or stack of containers is supported by contact of surfaces 1075 and 1077 on top.