PLUG buys fuel cells exclusively from BLDP
So when you see PLUG soaring up over 25% and BLDP up only 3.94%, it shows that many investors are clueless at who supplies PLUG their fuel cells.
Any contract wins by PLUG directly affect BLDP and therefore the stock price should also go in tandem with each other.
BLDP in my opinion is selling at a huge discount to what shares of PLUG are selling currently. That gap will close quickly as the word spreads on who is supplying PLUG.
See link it explains it all: