# Units of angle in comoving transverse distance calculation

For two objects at a redshift $$z$$, I know that the proper distance between them is given by $$\delta \theta d_M(z)$$, where $$d_M(z)$$ is the transverse comoving distance. What are the units of the angle out front? I know that $$d_M$$ has units of Mpc, but should the $$\delta \theta$$ be in degrees, radians, etc? And why is that the case?