There are 2 ABU Ambassadeur cog wheels 5152 and 23404.

5152 cog

Employed on 1500C, 2500C and older 4600-6600C reels before year 2000, and on some classic replicas. Spool shaft does not separate from spool. Some old Ultra cast design reels have the 5152.

5152 Cog is fastened by screw or E clip to the cog post, and please replace the original plastic cog to ball bearing cog.

23404 cog

Employed on most Ultra cast design reels like 4600C3 5600C3, 6500C3 or C4, C5. Spool and spool shaft are separate.

For the 23404 cogs, you'll need to cut the top of the gear to remove it from reel. The top of the cog is locking itself to the post groove, and it won't be removed even if you pull it hard, or you will break the side plate. To install the new cog or the original cog back to the reel, you'll need an E clip size 3mm. The clip is included to the ball bearing super 23404 cog kit.

• 
  top of the gear is locking inside to the shaft,
  and needs to remove
• 
  Cut only the top part with a very sharp knife
• 
  The cog post

• 
  remove the inside edge of cog
  if you want it perfect
• 
  Now you may re-install the cog to the post with an E clip.
  And enjoy installing tuning cogs.