Compression Adapter. The following glue into any 1/2 in. PVC fitting to make a compression fitting. Make your own custom fitting. Select for fitting size based on tubing size. 600 (green) fits 16 mm tubing (OD= .620") and 710 (blue) fits 1/2" ID & 18 mm (.710" OD tubing).  Note: 900 (gray) Fits 3/4" tubing (OD= .940") and glues into any 3/4" PVC fitting.