Pneumant wrote:What you have actually removed is the brompton seatpost shim, this is bonded into the frame and your seatpost won't stay in position without it! You will need to bond this essential part back in place. Don't even think of clamping up the seatpost without this part fitted!!
The height insert can only be fitted by removing the seatpost from the frame assembly, undo the saddle pentaclip and then pull <down> out of the frame bottom bracket end first. Once the seatpost is removed measure and cut the insert to size. The insert actually buts up against the part you have removed and determines max seatpost extension.
Ah, OK
On Youtube it looked like it fits inside the shim.