Shape System
From Brickwiki
The LEGO Shape System refers to a system of sloped elements (sometimes referred to as wedge bricks with curves) designed by Henk Holsheimer in 2000-01.
The primary motivation for this new group of elements was the need for smooth, curved shapes for upcoming Star Wars models.
All the elements in the system are designed to work together with some parts designed to fit over top of others.
References
- Brickjournal Issue 17, January 2012, pp. 71-73