Sixty under sixty
On this page14
The distribution
251 containers from 5 to 500 mL with a median of 177. 60 of them under 60 mL and 22 under 30.
Which is a usable small end
A dozen o rings of one size fit in 30 mL, and ten sizes of o ring want ten containers rather than one.
So the small end is the whole offering for this group
Ten named articles, each in several sizes, which is thirty or forty distinct parts in a domestic kit.
And the capacity buckets cluster usefully
29 containers at 59 mL, 8 at 15, 7 at 30, 3 at 5, 3 at 10 and 2 at 7. Which gives real choice below 60 mL.
The 5 mL end is almost too small
Three containers, and a 5 mL jar holds a few washers. Which for a single uncommon size is exactly right.
Above 60 mL the shelf is a different thing
47 containers at 237 mL and 44 at 118, which are jars for a quantity rather than a kit.
Which suits a trade buyer and not a householder
A plumber carrying a hundred of one washer wants the 237, and a householder with six wants the 15.
Diameter is the field for the fit
Published across most of the shelf, from 0.62 to 4.62 inches. An o ring has a diameter and so does the jar.
And a large flat part needs a wide mouth
A fender-sized washer or a large o ring will not go through a narrow neck, and the shelf runs 56 containers at 70-400 and 56 at 89-400.
Which are the two widest common finishes on this shelf
112 of 251 containers between them, so the wide mouth is well represented.
65 of 251 are full case only
With case packs from 12 to 6,370 and a median of 288. The 12 is what makes a one-part-per-jar kit affordable.
And 93 of 251 are quote only
So more than a third of the shelf has no published price, measured as a snapshot on one day.
Small, wide-mouthed and bought in twelves
Which is the shape of the answer for this group, and it has nothing to do with the statute.