NOTE: ANTIGRAV HOVERBOARDS DO NOT EXIST, so if you buy one it's a ripoff!
They will exist someday, but looking for antigravity devices today is like
asking for airline tickets in 1903. The "Wright Brothers" of antigravity
may be out there somewhere, but their invention isn't working yet, and
you'll have to wait for years (maybe decades) before genuine hoverboards
are for sale to individuals.
Some companies say they have "hoverboards", but these are just hovercrafts
(and they are HUGE, not the size of a skateboard.) Don't waste your money
on expensive "hoverboard" plans, instead try this one:
HOVERCRAFT PLANS (free!)