This is a model of Boy's Surface, a one-sided surface with no edges and no pinch points.
This is a modified version of Trapped Outside, without the cut-away track or internal ball. Shapeways treats the entire inside of this model as solid, hence the higher price.
The original design is here: http://www.shapeways.com/model/40473/trapped_outside.html
Without the ball: http://www.shapeways.com/model/237518/trapped_outside__track_.html
Solid, hollow inside: http://www.shapeways.com/model/233704/trapped_outside__solid_with_hole_.html
Remember to give this model five stars if you like it!
© 2011, Matt Chisholm. All rights reserved.