How about this, boots also get the bonus so the 4.5% lets your teir 1 boots give you the movespeed you would get with tier2 boots.
300 ms gives 13.5
50 from tier 1 gives an extra 2.5
70 from tier 2 gives 3.15
so your almost getting +1 tier boots. Combined with the 3% movespeed boost from utility mastery gives you
300 base gives +9
tier 1 boots give +1.5
tier 2 gives +2.1
So it adds up
mastery and quints makes you just a bit faster than the same hero with a tier higher boots.
If you have 330 Movement speed which I believe is the max base speed you get 344.85.
Generally those quints are only effective in premades when you have a Janna on your team.
If I remember properly w/o MS masteries on Ashe I go something like 314. and on Kayle w/ MS masteries I go 333 right off the bat.
As far as i know they turn your Mercurys into Swiftness.
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