I have bought a couple of the cheap helmets over the years...
I found them to work very well, However:
my only advise is to buy the SOLAR powered one that does not use batteries.
the battery ones have a power saver that keeps switching the helmet off and that is a pain in the butt!
ALSO....make sure the lens darkening control knob is on the outside of the helmet so you can easy adjust w/out taking helmet off.
ps: the solar unit works real good in low light conditions as well...