Mine was missing the pot and switch.
Also it did not work, after careful study I see the one that was shipped to me is used. PS, I have installed several of these.
Someone must have returned it.
I ordered this https://www.amazon.com/gp/product/B01HEXJUX8
Hope it is complete.

I put it on a very modified razor e300 so it can go to zero. (the razor just has a switch with a very slow soft.start ramp - not a true accelerator.)
Works great and barely gets warm. (250W motor... it's got headroom)
the separate pot and enable switch are just what was needed for my application.
the only thing i altered was to put a glob of silicone between each of the electrolytic caps to keep them from wobbling and possible breaking from repeated flexing of the wires - they are not sitting down tight on the board.

works well. no shorting or burning up.. does as it is advertised too.

Bought a 36volt golf cart with a resistive coil speed control and wanted to swap it for something solid state. Motor tag says 2hp(1500w). Really didn't want to spend $200 on a Curtis controller so I thought an $18 controller would be worth trying. Description says 60A, the power transistors it came with are rated at 90A continuous according to their data sheet, theres 8... I guess the other 4 drive those. So I fashioned up aluminum bars to bolt the terminals to since these are fairly small. 2 days of stress testing and it's still scooting. I've pinned it against a post and spun the tires. Tried gunning it fast to burn out. No problem. Motor emits a quiet PWM sound only at very low speed but I like it. The heat sinks warm up pretty fast but never got too hot. I'm probably going to add a fan just to be safe. Tempted to run it at 48v, but for now, this things a beast. All that's left is to make a pedal for the potentiometer. I'll try to add some pics when I have time.

Update: been using it for 2 months now. Probably every other day, including one very rough day where I was able to drag 4 incredibly HEAVY tree stumps about 50yards. It actually burned up part of the field coil on the motor! Had to have it repaired. So yes this speed controller will work great for a 36v 2hp golf cart. Potentiometer on mine is 20k ohms with a power switch, which can probably be wired to another switch. I was able to extend mine ~10ft using some Ethernet cable. Just ordered a $14 0-5v electric pedal, I think it's Hall effect and not potentiometer so we'll see if it works.

So I wired up this pedal... and left a review.
JCMOTO Foot Throttle Pedal Accelerator For Electric Go Kart Scooter E Bike (Black)

Completey bypassed the electronics on a 1992 brute force motorguide. And works far better than that old tech . Ran 6 hours with it on various setting and the heat sinks never got too hot to touch