Semroc Centering Rings Plywood Set 54mm to T-4.0 with 3 fins(3 ring set) CR-54mm-4.0P-3F
3 pack includes 1- slotted for fins and 2- Solid, no fin slots
ID= 2.26"
OD= 3.896"
1/8" lite plywood
With 3- 0.5" slots for inserting fins, slots are 0.125" wide
Made in the USA