The RLE (rear leg elevated) good morning is a single leg variation of the good morning that places more emphasis on hip stability than posterior chain strength.
 
Standing with a barbell on your back, place one foot on a bench or box behind you. Brace your trunk forcefully and hinge at the hips as far as you can without losing any extension in your back, unlocking the knees as you hinge. Stand again from the bottom without allowing the back extension to soften.
 
Purpose
The RLE good morning requires more stabilization at the hip, so is less effective for general posterior chain strength and more effective for improving hip stability and symmetry.
 
Programming
Sets of 5-8 reps are most common, but as many as 15-20 reps can be used, particularly in a rehab situation.