I have the P505 Base with the cranks from Magene. Price was $300 USD with free shipping. Installation was very simple. Straight swap from my Shimano 105 cranks, preload the non driveside and then a single pinch bolt. I'll post the weights below. So far, data has been tracking spot on with my Favero Assioma pedals except in one condition. It does not work well with oval chainrings...sort of. So my setup is a little weird. I do a round outer ring and an oval inner ring. This is why the Magene has problems. It's a well documented "issue" that spider power meters overestimate oval chainrings. Which isn't a problem in itself because you can adjust the offset of the PM. So if you're running a single ring oval, just can adjust it down to be accurate. Or if you're running 2x oval. The problem I'm having is that it's accurate for the round outer ring, but reads high when in the small oval ring. My solution is that I ordered a round inner ring. It's on the race bike and I wanted to get bigger chainrings anyways, so I'm fine with using round rings. The other option would have been to just know in my head that the readings were 10W off in the small ring, but my solution seemed simpler.
Overall, very happy with it. I wanted a cheap, accurate PM for my crit bike and this is it. Easy swap if you're running Shimano, and very accurate readings with round rings. I would buy again for sure. Magene is also making a pedal PM that looks promising but it's going to be a bit more expensive.
Weights
PM Spider: 112g
Driveside crank arm and spindle: 312g
Non driveside arm and preload bolt: 213g
Total weight (no chainrings): 638g
