What size are the threads for the spray tips?
The 12" Surface Cleaner & 14" Surface Cleaner have 1/8" Threads. The following models have 1/4" Threads: 14.5", 15", 20", and 21" Surface Cleaners.
The 18" Stainless Steel Surface Cleaner has an updated spray bar. The old spray bar (curved ends) has 1/8" threaded spray tips. The new spray bar has 1/4" threads. See image below for reference.