A sight for a firearm includes a housing, a tritium light source, a light transmission rod, and a retainer. The housing is configured to be mounted to a firearm. The tritium light source is supported within the housing. The light transmission rod is disposed in a cavity of the housing and positioned adjacent the tritium light source. The light transmission rod is configured to collect and transmit both an ambient light and a light from the tritium light source. The retainer is removably engaged with the housing and fixes the light transmission rod within the cavity. Removal of the retainer provides access for replacement of the light transmission rod.