Original white American Products Luxury scalloped 2 way diverter jet internal barrel dimensions - 108mmD Face x 53mmD Barrel have been replaced by the newer grey style with a larger face. Note that even the newer style are limited. Used by Monarch Spas and many others.
See images for comparison against newer replacement jet barrel. There may be issues with face diameter that may cause a problem with spa shell recesses around the jet. Please measure around your spa jet to make sure new style will fit. If they won't fit, your only option is to replace the entire jet body.