At last!  Now you can change your  existing pressure gauge on your D16/ D161 / D165 (in place of whistle) D18/ D20 /22. in place of existing pressdure gauge..This is a top quality  brass 1 inch in dia  0-30 pressure gauge with Wilesco adapter. Price is for pressure gauge and stem ony  NOT  engine. !  When filling engine take care not to overfill the boiler above 3/4 up the sightglass. This is as per instructions  but failure to do this will result in water getting into the pressure  gague rendering it useless!