The best replacement for spare is spair.

The best alternatives to spare are rated as following:
★★★★★  spair
★★★★★  strike
★★★★  kill slate
★★★★  baby back ribs
★★★  kill twinblade
★★★  kill saker
★★★  kill blacklist
★★  kill nouri
★★  kill reed
★★  back ribs
★  babyback ribs
★  baby back
★  kill reza nouri
★  kill jadid
★  dedicated hot spare
★  raid 6
★  spur of the moment
  extra
  standby hot spare
  kill fable 3
  kill slate bioshock

Your alternative for spare is not listed? Suggest!
Speaking about spare, one probably shouldn't forget about raid 6.

Other search terms related to spare and their ratings are:
★★★★★ raid 6
★★★ raid 1
★ key
You have in mind a companion for spare and it is not yet here? Propose!



Google Trends

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spare
spair
strike