The best replacement for tube is solid state.

The best alternatives to tube are rated as following:
★★★★★  solid state
★★★★  pipe
★★  tubeless
★  solid state amps
★  tubeless tires
★  transistor
★  solid state preamp
★  solid state bass amp
★  short tube headers
★  solid state rectifier
★  trabeculectomy
★  solid state guitar amp
★  shorty headers
★  g tube
★  g-tube
★  solid state amp
★  tubeless motorcycle tires
  j tube
  tubeless mtb
  solid state amplifiers
  transistor amp
  valve
  hose
  solid state guitar amps
  box subwoofer
  ng tube
  crew socks
  you tube
  tubeless motorcycle tire
  solid state bass amps
  solid state amplifier
  valve amp
  tight buffer fiber
  no feeding tube
  pan watercolors
  bundt pan
  goode t-tube
  monotube shocks
  tracheostomy
  water tube boilers
  nasogastric tube
  gastrostomy tube
  pipe definition
  tubeless tyres
  peg
  commercial
  not tube
  plate heat exchanger
  skylight
  expansion valve

Your alternative for tube is not listed? Suggest!
Speaking about tube, one probably shouldn't forget about handguard.

Other search terms related to tube and their ratings are:
★★★★★ handguard
★ cork
water seal
You have in mind a companion for tube and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of tube in all years. Click on graph for more.
tube
solid state
pipe