FYI, It took me a while to find enough really thin California Bell ones that would fit 21 or 22 to a barrel. I think out of 700+ $1 Cal Bell chips I've owned at one point or another, only about 160 of them were really thin bicycle tires. Most of the Cal Bell $1s are actually in good shape, and would not fit more than 20 to a 66.7mm barrel.
For the Sundance chips, just curious, how worn are they--will clean, unwarped, chips fit 21 (or even 22) in a 66.7mm barrel?