They might not be the best for speedsolving, but right out of the box the turning is so silky! Why is that?

No springs.

That can't possibly be the only reason, can it? >_>

No springs = less friction. The plastic is also fairly smooth when new.

Eastsheen plastic has some sort of micro-texture on it, like the lexan Cubesmith tiles only on a far tinier scale. Somehow, the texture decreases the surface contact area on a microscopic level, greatly reducing friction. I don't know how they do it; the plastic is not slick like most injection-molded parts, but it glides really nice. However, once the texture is ground away, the puzzle begins to lock up more often. Lube doesn't do much to improve an Eastsheen mech and only accelerates the wear process. Thusly, an Eastsheen turns best on day one right out of the box, but slowly gets worse over time with wear.

A Rubik's 4x4x4 or 5x5x5 (at least the older versions anyway, before they added rails to prevent disassembly) will not turn that good out of the box (lube helps a lot), but it is a solidly constructed cube with movement that becomes better with time as it "breaks in". My first Rubik's 5x5x5 tended to bind up a lot when I first got it in 2007, but with regular lubing and continued use, it got better and better with time, and even now I consider it one of my best 5x5x5s.

Precision manufacture helps. The parts are well made and, if all lines up, can move quite well. Puzzles with more sloppy manufacture will have friction in places where they should not because the shapes are not as perfect as they should be. This wears off over time, but it seems the ES production if very well done.

Dave

i had got the eastsheen set 2x2-5x5 and none of them really turned great out of the package except the 4x4, but with lubrication they all turn veryy smooth now. and probably no springs

Another possibility is the spindle mechanism - it doesn't have a ball core like many other 4x4s do, that's just for the 4x4. I don't have an Eastsheen 5x5 so I can't tell you about that

--JC--