Wellman ( WLM) fell after the polyester-products company swung to a loss in the most recent first quarter.

The company had a loss of $16 million, or 61 cents a share, compared with earnings of $11.6 million, or 22 cents a share, in the same period a year ago. Revenue totaled $342.7 million, down from $386.3 million last year.

Tom Duff, Wellman's chairman and chief executive, said in a statement that the company's first-quarter sales and earnings were hurt "by the surge in PET resin and polyester staple fiber imports that were caused by the increased raw-material cost advantage Asian polyester producers enjoyed compared to domestic producers during the latter part of 2005, primarily as a result of the Gulf Coast hurricanes."

Shares of Wellman sank $1.42, or 20.6%, to $5.48.

Monaco Coach ( MNC) took the high road after the Coburg, Ore., recreational-vehicle maker surged by Wall Street's first-quarter estimates.

Revenue increased 17% from last year to $385.1 million. Earnings rose to $8.3 million, or 28 cents a share, from $5.3 million and 18 cents a share, a year ago. Analysts were looking for earnings of 11 cents on revenue of $344.4 million.

For the second quarter, Monaco forecast sales of $375 million to $385 million, above analysts' consensus estimate of $352.4 million. Full-year sales are expected to be in the range of $1.45 billion to $1.48 billion, while Wall Street is calling for $1.41 billion.

Shares of Monaco rose $1.57, or 12.8%, to $13.82.

Keithley Instruments ( KEI) was advancing after the Solon, Ohio, electronic-instruments company beat analysts' second-quarter earnings expectations.

The company said sales rose 5% from a year ago to $39.7 million. Keithley earned $2.1 million, or 13 cents a share, including about $400,000, or 2 cents a share, in expenses for stock-based compensation. Last year's earnings totaled $3.2 million and 19 cents a share.

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