I need to change the stem seals on my car.

I know theres two types (one with a washer plate thing and one without)

but ive seen some advertised by PJ motorsport saying modified stem seals (£19.99)

any idea what they are?

do ford still do both types of seal and anyone have an approx price or can explain which applications have which type of seal?
cam fitted is supposed to be a piper t2 so not sure if I need a different type due to the springs or anything?

cheers