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.

Analysts were looking for earnings of 9 cents a share on revenue of $36.9 million. The company also estimated third-quarter sales of $37 million to $41 million.

Shares gained $1.26, or 8.6%, to $15.90.

Bell Microproducts ( BELM) saw its shares rise after the company posted an 8% increase in first-quarter revenue.

The company, a distributor of semiconductors, computer platforms and peripherals, said revenue reached $867 million, up from $804 million a year ago.

Earnings, excluding the effect of stock-based compensation expenses, totaled $2.9 million, or 10 cents a share. Including items, Bell earned $2.5 million and 8 cents a share, vs. $4.4 million and 15 cents a share a year ago.

Analysts surveyed by Thomson Financial were expecting a profit of 8 cents and revenue of $844.7 million.

For the second quarter, revenue is expected to be $810 million to $840 million, with earnings of 7 cents to 11 cents a share, excluding estimated compensation costs of roughly 1.5 cents. The consensus Wall Street targets are 7 cents for earnings and $827.7 million for revenue.

Shares of Bell were higher by 89 cents, or 15.6%, to $6.58.