The Mooer Slow Engine is a remake clone of the classic ridiculously expensive collectors item pedal the Boss Slow Gear SG-1 from the 80s. What this pedal did was help guitarists get the volume swell effect by silencing the attack of the guitar signal. Guitarists usually did this by hitting the string with the volume off on their guitar, then rolling it up immediately to get a violin type effect. Fantastically simple and sure to make your audience wonder how that sound is produced from a guitar. This all was pretty nifty, but it was also hard to pull off effectively and took a lot of coordination to get consistently live. Then Boss stopped producing them and now the old ones cost $350-500 on Ebay!
Then Mooer comes in and does us all a favor by recreating it faithfully and perfectly. You can tell it’s a faithful re-creation of the original down to the black outer casing, to the same naming of the knobs “sens” and “attack”, and even the naming is obvious “Slow Engine”
So save your $300, for a new, modern, lighter way to volume swell.