i have the 131's currently in my pump, i now have a set of 181's i was going to install with the 131 holders. but i would to know the purpous of doing this,

and i have a set of dv's that i removed from a john deere tractor that have102 marked on them and look like the 181's but the very bottom edges (the 4 corners) of the valve are rounded, the 4 slots go higher up the valve and the ring just above the slots is narrower than the 181's. looks to me like a step up from the 181's but does anyone know what the numbers mean on the dv,s?