This alloy seat post is 27.2mm in diameter, and 15.75 inch (400 mm) in length. It is made of aluminum.
People who are taller than 5’11” and shorter than 6’2 can buy this seat post to fit their RJ26A folding bikes.
To install your new seat post, use a 14 mm or 15 mm wrench (depending on your saddle adapter) to uninstall the saddle from the seat post. Then, take off the original seat post from the bike by unlocking the quick-release at the seat collar. Pull out the old seat post and put on the longer seat post. Make sure to insert the seat post all the way into seat tube, until you can no longer see the minimum insertion mark on the seat post. Put your bike saddle back on the seat post and use the 14 or 15 mm wrench to re-fasten the nuts. Then put the quick-release handle into a locked position at the seat collar. Enjoy your ride!
Enjoy your ride!