they just suggest that the sports are for lowering and not recommended for stock springs. but for the hd's it really depends on how low you want to go. the hd's are certainly adequate for lowering for sport/ street springs but not for slamming. they will be a bit softer than the sports so will offer a better ride quality than sports and are better for a daily driver. as a matter of fact i plan on using Touring class struts with hr oe sports. they are stiffer than stock shocks and are adequate for mild lowering.