Telescopic Seatpost for Tern GSD, HSD 34.9mm, will suit later Vektron which are also 34.9mm (Can be used to replace 'suspension type' NBD 34.9mm seatpost) These are quite a bit shorter than the standard Tern Telescopic 33.9mm, or the Tern BYB Telescopic 34.9mm as they are specific for the above Tern Models.