SPL Parts Porsche 991/981/718 GT3/GT4 Front Caster Arms w/anti diveSPL Parts Porsche 991 981 718 GT3 GT4 Front Caster Arms w anti dive Rubber should be saved for the tires. The factory front caster arms on Porsche 991 GT3 plus 981 and 718 Cayman GT4 platforms use soft rubber bushings that flex under load, which lets alignment and toe change right when you are asking the car to work the hardest. SPL Parts replaces those links with fully adjustable, spherical bearing components that keep the suspension honest and