This brush meets the specifications for use with any outdoor boiler with tube size 1.5". This includes model GX10.
For cleaning instructions of the GX series furnaces, see the video at this link:
Twisted and wire brush with 1.5” diameter and 36” overall 10 thousandths carbon steel w ½” ring on one end.
Please note: Do not turn this brush "counter-clockwise". Doing so may cause some of the brush bristles to fall out.