The critical dimensions for a replacement upright & yoke is the diameter of the bell bowl and the inside gap of the yoke. The inside gap is the distance across the yoke, excluding the end pins that rest in the open saddles of the upright.

If the bell is in the way and prevents an accurate measurement of the inside gap, we suggest a caliper to measure the inside gap without having to remove the bell bowl. A caliper can be made from two sticks to place one tip on one side of the yoke and another tip on the opposite side. Then grip the sticks firmly and place them on a ruler or measuring tape to determine the dimension, within 1/8th of an inch.