I had a tetra mattress in DS's bassinet (I didn't know about the snugglebeds 15 years ago!) and also bought him the pillow for when he was older in a cot. I bought it on recommendation from one of my cousins. We were in QLD at the time and it was hot, but the mattress seemed to stay cool, and the air can flow through it - it's breathable (if that makes sense?!).