Is this top warm enough to replace a blazer?

No. It is a lightweight polyester layer, so it adds polish and a little warmth but not the insulation of a lined wool or cotton blazer. Wear it over a long-sleeve top in cool weather.

Does polyester make it uncomfortable in summer?

Polyester does not breathe like cotton or linen, so it can feel warm and clammy in heat. It works better in air-conditioned offices or as an evening layer.

How should I wash it?

Polyester is easy-care: machine wash cold on a gentle cycle and hang dry. Avoid high heat in the dryer, which can set wrinkles and shrink the fabric.

What sizes are available?

It comes in S, M, L, XL and 2XL. Check the size chart against your bust and shoulder measurements, since polyester styles often run close to the body.