| Diameter reducer | Connecting a larger mouthpiece opening to a smaller port | A tapered or stepped insert bridges two openings of different internal diameters. | Measure both connection diameters and confirm the adapter’s insertion depth and seal style. | Useful when the available mouthpiece is wider than the device inlet. |
| Diameter enlarger | Fitting a smaller outlet to a larger mouthpiece connection | The adapter increases the connection size so the larger mouthpiece can seat on the smaller port. | Check that the smaller end fits securely and that the larger end matches the mouthpiece opening. | Allows compatible parts with different opening sizes to connect. |
| Threaded-to-slip adapter | Joining a threaded device port to a smooth, push-fit mouthpiece | One end screws into a matching threaded connection; the other accepts a smooth-fitting part. | Verify thread diameter, pitch, and gender. Similar-looking threads are not always interchangeable. | Combines a secure threaded connection with a simple removable mouthpiece. |
| Slip-to-threaded adapter | Connecting a smooth port to a threaded mouthpiece or accessory | A smooth end fits over or into the port, while the opposite end provides compatible threads. | Confirm the smooth-end diameter and the thread specifications on the other end. | Can add a threaded connection where the original port does not have one. |
| 510-style mouthpiece adapter | Devices and accessories designed around a 510-style connection | A 510-compatible base connects to a matching socket and provides a different mouthpiece interface. | Check that the device and adapter both use the same 510-style connection; this format is not universal. | Offers a replaceable connection option within compatible device systems. |
| Flexible silicone adapter | Minor size differences or connections that benefit from a flexible seal | A compliant sleeve stretches around a compatible port and helps hold the connected part in place. | Check the listed size range, material suitability, and temperature rating for the intended use. | Flexibility can accommodate small dimensional variations without rigid threading. |
| Angled or extension adapter | Changing the mouthpiece angle or adding clearance between parts | A bent or extended passage redirects the connection while keeping the two components joined. | Check the angle, overall length, connection sizes, and whether the added path affects airflow. | Can improve clearance when a straight connection is awkward or obstructed. |