Bulls NL
Bull's NL - use with Aluminium Shafts - O Ring Applicator with O-Rings (6) | Darts Corner UK
£2.30
https://www.dartscorner.co.uk/ Go to shop Description
Accessories - Bulls Oring Applicator. Includes 6 O Rings. Use this simple tool to apply the little orings to your aluminium stem to help ensure the stem does not work itself loose.