I started out with Suntour NCX SP-12 on my hard tail Radrover back in 2017. It comes in 350mm or 400m post lengths for the 27.2mm size AND Hard red springs (+195lbs; but, not sure of max weight) or Soft blue springs (140-195lbs). Noticed a few Suntour NCX are shown with gray colored spring and I couldn't tell if it was the hard, soft, or something else? I purchased used off eBay back then and they could have been a fake? It still performed to my satisfaction with zero issues for years.
Suntour was very comfy for me with the Cloud-9 cruiser saddle over most uneven to undulating dirt and paved surfaces. You do still feel minor bumps like vibrations, potholes, broken pavement, uneven side walk cracks, and washboard dirt trails because you are still sitting on top of spring connected to your saddle and frame.
PDF to spot a fake Suntour if purchasing used or 3rd party:
I later swapped to Kinekt Bodyfloat suspension seatpost in 420mm length a few years later. You can purchase different springs combinations to better match your weight from 80lbs to 320lbs. The Kinekt felt better than the Suntour with the minor bumps because the (e)bike floated under you to help isolate even better from vibrations, minor bumps like pothole, sidewalk cracks, washboard dirt trails, etc... It made my hardtail Radrover feel closer to a full suspension ebike. Noticed I didn't have to lift off my seat as much with the Kinekt seatpost when riding over hundreds of bumps/curbs/cracks/potholes you encounter when riding. That made it less fatiguing on long rides. I added Kinekt to the wife's Radcity step-thru and she felt the improved ride instantly compared to standard seatpost+Cloud-9 (the Suntour NCX head was too tall for her at 4'11" to use).
The HUGE downside with Kinekt is the prices between $270-$350. I added a locking seatpost clamp and a protective wrap for both ebikes.
