I recently bought Item #14303 and would say it is medium weight perhaps toward lightweight. The specs show product weight is 8.2 oz. Compare that to Item #3886Y Valde Merino Wool Base Layer Top - Short Sleeve (For Men) Weight: 4.5 oz. It would seen that the long sleeves of 14303 wouldnâ€™t account for that much difference if the material density per square foot is the same. I bought both these items and compared them by viewing through them out my window. The 14303 seems a bit tighter weave. I got it for colder use and the short sleeve shirt for summer.