spring #'s

[Deuce4935]

Can someone please break the following spring numbers down for me please. I dont understand why the springs that are designed for non a/c and are non heavy duty springs have a taller height than the ac heavy duty springs.

RAYBESTOS Part # 5851166 {Professional Grade; Sold in Pairs -- Inside Diameter=4.09" Wire Diameter=.672" Free Height=15.63" Load height=11"}
Front; Except Air Conditioning; Automatic Overdrive Transmission (Only 2 Remaining)

$69.79 $0.00 $69.79
RAYBESTOS Part # 5851151 {Professional Grade; Sold in Pairs -- Inside Diameter=4.09" Wire Diameter=.672" Free Height=15.88" Load height=11"}
Front; Air Conditioning; Automatic Overdrive Transmission (Only 2 Remaining)

$69.79 $0.00 $69.79
RAYBESTOS Part # 5851111 {Professional Grade; Sold in Pairs -- Inside Diameter=4.08" Wire Diameter=.687" Free Height=14.63" Load height=11"}
Front; Except Air Conditioning; Automatic Overdrive Transmission; Heavy Duty

RAYBESTOS Part # 5851110 {Professional Grade; Sold in Pairs -- Inside Diameter=4.08" Wire Diameter=.687" Free Height=14.88" Load height=11"}
Front; Air Conditioning; Automatic Overdrive Transmission; Heavy Duty (Only 4 Remaining