To replace the tenon between the bass joint and the bell. This is only for one although it's a picture of three.
Vintage Ferrees G52A Replacement Tenons For Bassoon
Vintage Ferrees G51C Replacement Tenon For Bassoon
Vintage Ferrees G72B Grenodillo Plastic Tenon Plug For Soprano Clarinets
Vintage Ferrees G73B Grenadilla tenon plug For Bb Soprano Clarinets
Vintage Ferrees G72E Grenadilla Tenon Plug Fro Bass Clarinets
Vintage Ferrees G72A ABS Plastic Tenon Plug For Soprano Clarinets