Hoppe  20mm Top Extension for Manual Shootbolt Version.   
The top shootbolt extension is used with different middle extension to achieve overall door height.

Faceplate Width: 3/4 inch  (20mm) .787 inch 
Top Extension length: 21.65 inches ( 550mm)
Maximum Cutoff: 3.94 (100mm) inches. 
Number of screws: 4
Material: Stainless Steel 

The Top Shootbolt Extension can be combined with five different middle extensions lengths.
Each is used to achieve different overall door heights.
20mm MIDDLE EXTENSIONS -
2185977 - Length 7.52 inches (191mm) 
2424131 - Length 17.36 inches (441mm)
2186523 - Length 27.20 inches (691mm)
2185951 - Length 44.92 inches (1141mm)
2185934 - Length 62.64 inches 1591mm)