Brompton G Line Handle Bar Catch Assy
 
It is not compatible with the A, C, P or T Line Brompton bicycles 
 
This kit comprises the following: 
G Line handlebar catch assembly
Serrated washer for the handlebar catch assembly 
Flat washer for the handlebar catch assembly 
Bolt for the handlebar catch assembly
G Line handlebar nipple
2 x flat washers for the nipple
1 bolt to hold the nipple in place
 
This is one of the "Brompton Essentials" - a part necessary to keep your Brompton folding as it should.
In a properly set up Brompton, the final part of the fold should be to undo the clamp holding the stem into place and the handlebar assembly will drop down and clip into the catch automatically.