This is an 1.5 inch side mounted air inlet for a UDS Smoker. The round flange is bent to match the profile of the side of the drum. This is a ready to bolt on part. Simply drill a 1.5 Inch ID hole in the side of your drum about 3 inches up from the bottom and bolt it to the side of your drum. We recommend you drill the holes and test fit it to your drum then take it apart and paint it. After you paint the drum and the parts install the part on your drum and use a thin bead of High temp silicone under the flange to seal it.