This is the most common carriage wheel in Accordion Shutters today.
It is sold in packs of 20, 40, 60 or 100.
Carriage Wheel Small Center Hole (Pack of 20)
$22.00Price
The hole for this carriage wheel is 5/16" diameter. The outside width from wheel to wheel is 1 1/2" (see pictures). It's used in most accordion shutters currently.