Flex3 / Flex4 components correspondence

Flex3: mx.controls.ComboBox spark.components.DropDownList (w/o editability)
Flex4: mx.controls.HorizontalList spark.components.List (with a HorizontalLayout)

Flex3:  mx.controls.ComboBox
Flex4: spark.components.DropDownList (w/o editability)

Flex3: mx.controls.HorizontalList
Flex4: spark.components.List (with a HorizontalLayout)

Flex3: mx.controls.HRule
Flex4: spark.primitives.Line
Flex3: mx.controls.VRule
Flex4: spark.primitives.Line

Flex3: mx.controls.Image
Flex4: spark.primitives.BitmapImage (w/o support for external images)

Flex3: mx.controls.LinkBar
Flex4: spark.components.ButtonBar (with a custom skin)
Flex3: mx.controls.ToggleButtonBar
Flex4: spark.components.ButtonBar

Flex3: mx.controls.LinkButton
Flex4: spark.components.Button (with a custom skin)

Flex3: mx.containers.ControlBar
Flex4: spark.components.Panel (with the controlBarContent property)
Flex3: mx.containers.ApplicationControlBar
Flex4: spark.components.Application (with the controlBarContent)

Flex3: mx.containers.Canvas
Flex4: spark.components.Group

Flex3: mx.containers.Tile
Flex4: spark.components.Group (with a TileLayout)
Flex3: mx.controls.TileList
Flex4: spark.components.List (with a TileLayout)

Flex3: mx.containers.HBox
Flex4 spark.components.HGroup
Flex3: mx.containers.VBox
Flex4: spark.components.VGroup

Flex3: mx.controls.VideoDisplay
Flex4: spark.components.VideoPlayer


[ref]
http://www.adobe.com/devnet/flex/articles/flex3and4_differences.html#_Namespaces_and_packages