J.Crew Women's Tissue Turtleneck Tee - Soft Slim Fit Long Sleeve Cotton Top for Layering, Work & Casual Wear

The collars in a size small stay up but not in size medium.I have the small in the olive but the navy size small was a bit more snug than I prefer so I returned it for a medium and love that it's a little loose. For reference, am 5'9" and ~125lbs.Great pattern. So comfortable!