Can I use a polydimethylsiloxane (PDMS) coated stir bar with OPTIC?

Yes, most of the stir bars used have an OD of 3.2mm and the OPTIC standard fritted liner has an ID of 3.4mm.

The OPTIC 1/4 inch version has an ID of 4.0 mm. There is a special liner available2414-1105, 1/4 x 3.5 inch Glass Liner for Sorptive Sample, pk/5.