Plastruct Concrete Block (2) HO

What is this item and exactly what kit is it utilized with?
Where is the part located on the kit?

FEATURES:
(What makes this item different, color, construction, product?)

INCLUDES:
(How many do you get? Make a list of if more than one part.)

NEEDS:
(What else does this item need to make it work?)

SPECIFICATIONS:
Length:
Width:
Height:
Diameter: (If suitable)

COMMENTS:
(Any unique application or something it will not work with?)