The best replacement for seatpost is alloy.

The best alternatives to seatpost are rated as following:
★★★★★  alloy
★★★  longer stem
★★★  carbon
★  carbon seatpost
  aluminum seatpost

Your alternative for seatpost is not listed? Suggest!
Speaking about seatpost, one probably shouldn't forget about carbon frame.

Other search terms related to seatpost and their ratings are:
★★★★★ carbon frame
You have in mind a companion for seatpost and it is not yet here? Propose!



Google Trends

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seatpost
alloy
longer stem