Word on the street is that KADO-KESHI, simply "corner eraser", has 28 staggered cubes on it. Ok, it looks really cool, but thanks to this unique shape, you can erase small parts accurately and fully. As the eraser decreases from use, you can still use the the bits that break off.

Since its first release in 2003, this best-selling Japanese eraser took many prototypes before arriving at its present not-too-soft and not-too-hard formulation. 

Made of styrene-based elastomer resin.

Measures 0.8" x 2" x 0.8" (20x50x20mm)