Is it considered an undershirt or a regular shirt ?

My husband considers it an undershirt, wears it under his dress shirt. It's a bit thin to wear as a regular t-shirt.

Where are these IQ t shirts made?

Hello, these IQ T-Shirts are made in the Dominican Republic.

Are these super thin tshirts?

Yes, they are super thin and the texture is not soft. Shrunk like crazy. It's not the same like what Hanes used to make.

What's in a cotton tee to have a prop65 warning? >"this product contains chemicals known to the state of california to cause cancer and birth defects"

Do NOT ignore the Prop65 warnings. It means that there is something present above the “safe harbor level” that could cause cancer or cause reproductive and developmental effects. They have to do a risk assessment that takes into account the potential exposure of the chemical and toxicity of the chemical. It is not true that everything has it. It is not wise to ignore a warning that would only be present because it is mandated because it exceeds safe levels. It is likely for this product that it was treated to sterilize the product - it could be formaldehyde, ethylene oxide, or ?. I would wash the shirts before wearing them for the first time. I wish the warning included the chemical of concern and how much is present…. Google “prop65” and “consumer safety concerns” and “risk exposure” for more information.