These are the shaft end bushings to prevent wire or string from getting off the end of the shaft. Adhesive attached. Kit comes with two bushings and four cotton swabs for cleaning prior to attachment.
Bonding surfaces of the Bot should be cleaned with IPA soaked swab, then wiped dry with second clean swab. Then peel masking from adhesive side of bushing, flexing open to insert around the shaft, then pressing in place and hold for 10 seconds for adhesive to set.
These are limited and not always available.