PAC sometimes moves faster than the industry in valve spring technology.   Case in point, the PAC-1335, the first LS solid roller spring to fit stock heads, has been around since 2010.  Since then, the product line has expanded along with engine platforms.  These springs are an excellent upgrade choice in any engine platform running a solid roller type lifter.  Being able to maintain similar loads to the 1.500" and 1.550" while shaving 30% mass.