This is a vacuum hose coupler for the Dewalt DWS713 Miter Saw. You can easily connect your portable vacuum to the saw's dust collector port with this 32mm to 42mm cylindrical coupler. It has a small internal edge that prevents the coupler from sliding completely onto the 32mm vacuum hose.
In later use of the coupling, I discovered that a problem could arise if there was not enough space behind the saw for the rigid part of the vacuum hose. To solve this I redesigned it with a bend so it can mate directly to the flexible hose bypassing the rigid part.
After a few years of use, it was also discovered that even the curved piece could crack easily. To improve this, I have reprinted the coupler using a flexible filament, after which I have had no problems.