All solo seat springs that I know of are sold with quite shoddy chrome plating. Most are too soft to endure a heavy passenger and or bumpy roads. And as far as I know, none seem to be manufactured in the USA.
Remedy? Bare Knuckle Choppers is launching 3″ stainless steel seat springs (no more worry about chrome), 20% stiffer than the run of the mill springs out there (no more bottoming out) and made here in the USA (feel good factor)
Electropolished version will be available soon, and will run you a couple extra bucks. Price? Only $15. Call Paul Wideman on my behalf at 1-888-240-NUKL. Bare Knuckle Choppers.