diff --git a/adcom1/expandable_direction.go b/adcom1/expandable_direction.go
index 135800c..48fc30b 100644
--- a/adcom1/expandable_direction.go
+++ b/adcom1/expandable_direction.go
@@ -10,5 +10,5 @@ const (
 	ExpandableUp         ExpandableDirection = 3 // Up
 	ExpandableDown       ExpandableDirection = 4 // Down
 	ExpandableFullScreen ExpandableDirection = 5 // Full Screen
-	ExpandableSmaller    ExpandableDirection = 6 // Resize/Minimize (make smaller)
+	ExpandableResize     ExpandableDirection = 6 // Resize/Minimize (make smaller)
 )
diff --git a/adcom1/placement_position.go b/adcom1/placement_position.go
index 5cc6fc0..2939d43 100644
--- a/adcom1/placement_position.go
+++ b/adcom1/placement_position.go
@@ -6,6 +6,7 @@ type PlacementPosition int8
 
 // Placement positions.
 const (
+	PositionUnknown    PlacementPosition = 0 // Unknown
 	PositionAboveFold  PlacementPosition = 1 // Above The Fold
 	PositionLocked     PlacementPosition = 2 // Locked (i.e., fixed position)
 	PositionBelowFold  PlacementPosition = 3 // Below The Fold
@@ -14,3 +15,16 @@ const (
 	PositionSideBar    PlacementPosition = 6 // Sidebar
 	PositionFullScreen PlacementPosition = 7 // Fullscreen
 )
+
+// Ptr returns pointer to own value.
+func (p PlacementPosition) Ptr() *PlacementPosition {
+	return &p
+}
+
+// Val safely dereferences pointer, returning default value (AdPositionUnknown) for nil.
+func (p *PlacementPosition) Val() PlacementPosition {
+	if p == nil {
+		return PositionUnknown
+	}
+	return *p
+}
diff --git a/openrtb2/banner.go b/openrtb2/banner.go
index 7c6b76c..7277cfd 100644
--- a/openrtb2/banner.go
+++ b/openrtb2/banner.go
@@ -1,6 +1,10 @@
 package openrtb2
 
-import "encoding/json"
+import (
+	"encoding/json"
+
+	"github.com/mxmCherry/openrtb/v16/adcom1"
+)
 
 // 3.2.6 Object: Banner
 //
@@ -76,19 +80,15 @@ type Banner struct {
 	//   NOTE: Deprecated in favor of the format array.
 	//   Minimum height in device independent pixels (DIPS).
 	HMin int64 `json:"hmin,omitempty"`
-	
+
 	// Attribute:
 	//   btype
 	// Type:
 	//   integer array
 	// Description:
 	//   Blocked banner ad types.
-	//   Values:
-	//   1 = XHTML Text Ad,
-	//   2 = XHTML Banner Ad,
-	//   3 = JavaScript Ad,
-	//   4 = iframe.
-	BType []int8 `json:"btype,omitempty"`
+	//   Refer to BannerAdType constants.
+	BType []BannerAdType `json:"btype,omitempty"`
 
 	// Attribute:
 	//   battr
@@ -96,7 +96,9 @@ type Banner struct {
 	//   integer array
 	// Description:
 	//   Blocked creative attributes. Refer to List: Creative Attributes in AdCOM 1.0.
-	BAttr []int64 `json:"battr,omitempty"`
+	// Note:
+	//   OpenRTB <=2.5 defined only attributes with IDs 1..17.
+	BAttr []adcom1.CreativeAttribute `json:"battr,omitempty"`
 
 	// Attribute:
 	//   pos
@@ -104,7 +106,7 @@ type Banner struct {
 	//   integer
 	// Description:
 	//   Ad position on screen. Refer to List: Placement Positions in AdCOM 1.0.
-	Pos *int8 `json:"pos,omitempty"`
+	Pos *adcom1.PlacementPosition `json:"pos,omitempty"`
 
 	// Attribute:
 	//   mimes
@@ -131,7 +133,9 @@ type Banner struct {
 	// Description:
 	//   Directions in which the banner may expand. Refer to List: Expandable
 	//   Directions in AdCOM 1.0.
-	ExpDir []int8 `json:"expdir,omitempty"`
+	// Note:
+	//   OpenRTB <=2.5 defined only directions 1..5.
+	ExpDir []adcom1.ExpandableDirection `json:"expdir,omitempty"`
 
 	// Attribute:
 	//   api
@@ -141,7 +145,9 @@ type Banner struct {
 	//   List of supported API frameworks for this impression. Refer to List: API
 	//   Frameworks in AdCOM 1.0. If an API is not explicitly listed, it is assumed
 	//   not to be supported.
-	API []int64 `json:"api,omitempty"`
+	// Note:
+	//   OpenRTB <=2.5 defined only frameworks 1..6.
+	API []adcom1.APIFramework `json:"api,omitempty"`
 
 	// Attribute:
 	//   id
diff --git a/openrtb2/banner_ad_type.go b/openrtb2/banner_ad_type.go
new file mode 100644
index 0000000..35bef24
--- /dev/null
+++ b/openrtb2/banner_ad_type.go
@@ -0,0 +1,13 @@
+package openrtb2
+
+// BannerAdType
+//
+// Types of ads that can be accepted by the exchange unless restricted by publisher site settings.
+type BannerAdType int8
+
+const (
+	BannerAdTypeXHTMLTextAd   BannerAdType = 1 // XHTML Text Ad (usually mobile)
+	BannerAdTypeXHTMLBannerAd BannerAdType = 2 // XHTML Banner Ad. (usually mobile)
+	BannerAdTypeJavaScriptAd  BannerAdType = 3 // JavaScript Ad; must be valid XHTML (i.e., Script Tags Included)
+	BannerAdTypeIframe        BannerAdType = 4 // iframe
+)