The BOSS RPD-10, released in 1987, is a stereo digital delay effect unit and a rather rare effect in BOSS's "Micro Rack Series," a half-rack size series. It allows you to set the delay time in 8 steps, from 15ms to 2s, and you can fine-tune the length with the "FINE" knob. A notable feature is the "TONE" knob, which has a blue-filled zone. In this zone, you can maintain the feedback feel of the delay just before it starts to howl, and turning it further causes self-oscillation. The sound quality is three-dimensional and has a sense of depth, making it a highly functional effect unit not found in compact effectors. I have connected it to an adapter and checked the power and sound. It is a fully functional item with few scratches, but it is old equipment, so please understand that it is non-refundable and non-returnable.