Buying a class set
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Thirty identical units
Which is the specification most catalogs ignore. A set where two units differ produces results a class cannot compare, and the lesson is about comparison.
Reorderable is the second requirement
A class set is replaced over years, a few at a time. A container that is discontinued leaves a cupboard with two incompatible generations in it.
Which argues for the big families
101 PET single wall jars, 78 glass Boston rounds, 48 PE cylinder rounds, 42 HDPE packers. A format with many sizes in it is a format likely to still be here.
Stackable, because the cupboard is the constraint
Straight sided containers pack without gaps. A tapered bottle wastes shelf depth, and in a shared prep room the shelf is the scarce resource.
One neck across the set
51 containers at 24-410, 38 at 70-400, 34 at 89-400. One bottle neck and one jar neck across a whole cupboard means one box of spare caps rather than five.
Budget for spare closures from the start
Caps go missing in a classroom in a way they do not in a laboratory. Ordering half again as many closures as containers is realistic rather than wasteful.
Label area that a marker will take
If writing on the container is awkward, the set ends up unlabelled. A matte panel or a surface a pen marks is what makes labeling actually happen in a thirty minute lesson.
Impact resistance where it can be had
Glass where the chemistry needs it and a polyolefin where it does not. The 150 jars include both, and the decision is per experiment rather than per cupboard.
Volume that matches the exercise
71 containers at 30 mL or under and 211 at 120 or under. A class exercise rarely needs more than 120 mL, and buying bigger wastes reagent as well as space.
And one container that is obviously not food
In a building full of children, a reagent in something that looks like a drinks bottle is a standing risk. Choose the format that does not invite the mistake.