AXT550 is a 2K spray putty hardener (activator) used in automotive refinishing systems — most commonly in Cromax sprayable polyester putties like 799R.

What it is

• Full name: AXT550 Hardener for 2K Spray Putty
• Type: polyester spray filler activator (hardener)
• Used in sprayable body fillers / spray putties, not clears or primers

What it’s used for

AXT550 is mixed with spray putty systems such as:

• Cromax 799R sprayable putty
• Similar 2K polyester spray fillers

It helps the product:

• Chemically cure and harden
• Build a sandable surface layer
• Fill minor imperfections, sanding marks, and waves