$ROKU calls up 5-fold in a day

It took just one session for bullish option traders to score huge profits in Roku (ROKU).

Just yesterday, Our tracking systems found that 4,500 Weekly $155 calls expiring this Friday were purchased for $1.81 to $3.30 above open interest of 2,152 contracts as part of a bullish spread with shares at $153.60. Co-founder Jon Najarian cited the unusual activity at that time on CNBC’s “Halftime Report.”

Those calls have traded up to $13.18 so far today, more than 5 times their average purchase price. The stock rose 9% at the same time, illustrating the kind of leverage that can be achieved with options.

Long calls lock in the price where a stock can be purchased, gaining with a rally and providing leverage to the underlying shares. The contracts can quickly lose value if the stock stalls or pulls back but also carry less risk than owning the shares themselves.

It is the second winning trade in the name posted on Unusual Option Activity in the last month.

ROKU is up 6.02% to $166.33 in midday trading. DA Davidson raised its price target on the video-streaming company to $185 from $135 this morning.