$PRLB is one of biggest losers #stocks today. read more:

Proto Labs, Inc. Common stock (symbol: PRLB) was one of the worst losers of
the trading day today (2016-08-31), losing -7.97%. The number of shares
that changed hands was 924,628, or about 3 times the average daily volume
in the stock.
The closing price was $54.72, amounting to a market cap of $1,450,000,000,
about -33.32% off the highest price in the last 12 months. The stock has
been trading at a range between $50.5 and $82.06.
PRLB is in the Metal Fabrications industry, part of the Capital Goods
sector. It first went public in 2012.
Looking at its valuation, the stock is now trading at 31.65 times earnings.