The two subatomic particles that have a mass of about 1 amu are:

* Protons: These particles have a positive charge and are located in the nucleus of an atom.

* Neutrons: These particles have no charge (they are neutral) and are also located in the nucleus of an atom.

While the actual mass of both protons and neutrons is slightly more than 1 amu, they are commonly rounded to 1 amu for simplicity in calculations.