is 6 on a and 5 han after a call. Every tile is one suit. An honor removes it.
The name players use is chinitsu (清一色). This site's glossary also lists it as Full Flush. Players also call it a full flush.
One suit, no honors
Every tile is , , or . A second suit removes the yaku. One honor turns the hand into honitsu: 3 han closed and 2 han open.
The tiles are manzu. Triplets of 1, 2, and 3 are finished. The rest is 78 and a pair of 9s. The hand waits on 
or . finishes 678. finishes 789. The pair of 9s stays either way.
Closed or open
The EMA 2016 list files full flush with the 5 han yaku, and adds one han when the hand is concealed. That is the same pair of numbers as the row on this site: 6 closed, 5 open. A , a , or an is the open case.
The glossary entry is the short form: one numbered suit, 6 han closed and 5 han open.
What 5 han pays
Five han is a , whatever the fu. An open chinitsu with no extra fu is 20 fu, and that rounds up to 30. At 5 han, a collects 8,000. The dealer collects 12,000. Those payments have no and no sticks.
A closed hand is 6 han from this yaku before and before any other yaku. Six han is a . A non-dealer ron collects 12,000. The dealer collects 18,000. A tsumo on a closed hand also has menzen tsumo.
What sits with it
Tanyao sits in the same hand when every tile is 2 through 8. Toitoi sits in it when the four sets are triplets or quads.
Price a chinitsu hand
The score calculator turns 5 han into a mangan and 6 han into a haneman. A closed hand starts at 6 han.
Open the score calculator