Stocks in the 3-D printing sector, such as Stratasys and 3D Systems, represent an easy target for lower expectations after an epic run-up during last year's surging stock market, CNBC's Jim Cramer said Monday.
In fact, the 3-D printing space has become home to the "most hideous" stocks in the market right now, according to technicians, Cramer added. Shares of both Stratasys and 3D Systems saw huge price spikes in the past 12 months, before witnessing steady declines in recent weeks.
3D Systems shares, for example, almost doubled in price during the past year, caught up in investor hype about the prospect of 3-D printing technology spurring a commercial and industrial revolution.
Long-term stock market prospects, however, don't bode well, Cramer said. In November, Cramer called the 3-D printing sector a bubble despite rapidly rising share prices among the industry's flagship companies.
"This area was so much in favor that they can fall further," Cramer said on "Squawk on the Street." "But again, these are real businesses. They're just overvalued."
Cramer said he was also concerned about "raw enthusiasm" driving up biotech and fuel cell stocks, highlighting Plug Power as a company in which he receives an inordinate amount of interest among his Twitter followers. Investors have also shown a disconcerting level of adoration for the stock, which has risen sixfold in the past year.
Plug Power shares moved even higher Monday morning off news that it had signed a contract with Wal-Mart to provide batteries for its warehouse machines. Cramer said investors "are piling into a name they do not know or understand." Fuel cell stocks such as Ballard Power Systems and FuelCell Energy have also seen significant share price increases.
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"That does worry me," Cramer said. "You tend to see that level of enthusiasm, and it tends not to be a bottom. At the same time, if you can cordon it off, the more areas you can add to that kind of bubble, the less conviction you have. ... These are bad signs."
Cramer sees the same pattern in the biotech sector, he said.
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"Take a look at a lot of the parabola in the biotech stocks," Cramer said. "A lot of them have nothing to do with approvals. It's just raw enthusiasm."