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Product Description
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.
Other versions:
The original design is here: https://www.shapeways.com/model/40473/trapped_outside.html
Without the ball: https://www.shapeways.com/model/237518/trapped_outside__track_.html