Aspen Aerogels (ASPN) said late Monday it priced an underwritten public offering of about 4.3 million common shares at $20 each for expected gross proceeds of about $85 million.

The company granted the underwriters a 30-day option to buy up to an additional 637,500 shares. The offering is expected to close Wednesday.

Aspen plans to use the net proceeds for working capital, capital expenditures and general corporate purposes.

Aspen Aerogels shares dropped more than 4% in premarket activity Tuesday.

Price: 20.45, Change: -0.88, Percent Change: -4.13