A straight-thru fitting to adapt a 1.5" dust port to a 2.5" (nominal) hose, or vice-versa. See the build log here for more details and dimensions: jmillerid.com/wordpress/2012/12/3d-printed-shop-vac-adapter/ NOTE: this is derived from my 90 degree elbow version. This one is straight but uses the same fitting dimensions (see the attached image, these are inside dimensions), and does not require support material!