In-Active Top Shootbolt Extension, used on 3 piece Inactive Version Shootbolts 

Extension Length: 19.25
Maximum Cutoff: 4.5 inch
Number of Screws: 3
Overall Length w/ 36 handle Height: 69.76 -73.70 Doors (if used as top extension)

NOTE 1:
This is also used on the adjustable handle height active shootbolt #3664566 (35/92) 
Use Inactive (IA) Top or Bottom Shootbolt extension for Adjustable Handle Height versions

Note 2: 
Inactive and Active shootbolt extensions work differently and are NOT interchangeable. 
Inactive shootbolts Push to Extend Bolt
Active shootbolts Pull to Extend bolt