SPRING RATES
On our Revo-A Softail Mono Shock 2018+, if the spring is labeled "Legend 450" this is the Standard-Duty Spring, and "Legend 550" is the Heavy-Duty Spring.
NOTE: Heavy Duty applications are recommended for 350lb + rider and passenger total weight. Also consider Heavy Duty if the majority of your riding is 2 up with a passenger and/or gear.