Firstly, please don't bash me for my english, I am a native Chinese speaker(And a asian). Ok, so many speedcube reviewer said the grooves on moyu and gans puzzles(357) are for reducing friction, but many of them got it wrong when they say that it reduces surface area. now, if you learnt before, surface area does not determind friction, so what the grooves does is act like a 导油槽, it is to hide the extra lube and reduce static friction, so when you put too much lube, it actually get hidden in the groove and will not be rubbing between pieces, reducing static friction. Hope i clear that misconception