I have a small wheeled electric bike, because it is electric, the bike frame is very strong and rigid, that coupled with small tyres means that the ride is harsh on anything else but smooth surfaces, so I decided to try one of the suspension seat posts. You will need to take the existing post out to find the size that you require, this is stamped into the metal, usually in mm's, you should also note the length of the shaft.
When the unit arrives, fit you seat, and maybe try and move the seat forward as sitting directly above the seats gives the best suspension movement. On the base of the new shaft is a small hole for spring adjustment, I had to undo this by a few turns before the spring would move when I sat on the seat, but once you have tuned this to your weight and riding position, the ride on the bike is much improved. For the money, its worth a try!