We learned it while engineering six machines, each feeding one part size; 1-1/4 to 1-3/4 inch diameter.
We found they resisted movement in enclosed tracks, so all paths were kept open and free in the orientation effort.

When final tracking was needed only one part-at-a-time was passed with a puff of compressed air.
Gravity or vibratory tracks were a NO-NO with these flexible, rubber like parts.

We provided two paths to assembly at 16 pieces per minute; far below 78 dB(A) at 3 feet.

Since they were for automatic transmissions, it required all part contact surfaces to be stainless steel,
plastic or specially plated steel to avoid contamination.