1N5821RL is a Schottky rectifier diode from On Semiconductor rated for 30V reverse voltage and 3A forward current, packaged in an axial lead DO-201AD case.
The 1N5821RLG is a 30V, 3A Schottky barrier rectifier from On Semiconductor featuring a low forward voltage drop of 500mV at 3A. It is supplied in an axial lead DO-201AD package for through-hole mounting.