A prefab? Pre-fabricated granite, commonly known as "prefab,"  is precut granite/Quartzite/Quartz/Marble with finished edge details for mass production, ready to install.   
Prefabs sizes           
26" x 110"                  
36" x 110"
42" x 110"
52" x 110"               

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Quartz
A man made material, quartzite and a resin mix combined make up a quartz shape and durability.

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Marble
  A metemorphic rock composed of minerals. The softest of the 4 materials, can be polished or honed.  Being typically white with mottlings or streaks of color.

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Quartzite
Consisting of mostly quartzite, a natural stone, it is the hardest material of the four. Color range is limited to stone characteristics.

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Granite
 A common type of rock that is granular and phaneritic in texture. Granites can be predominantly white, pink, or gray in color.