RadQual’s Spot Markers are reference sources manufactured by gravimetric transfer of Na-22 or Ge-68 sealed with an epoxy mixture and checked by ion chamber for content. There are two designs available. The traditional Lucite marker with a total diameter of 1.0 inches (2.54 cm), an active area of 0.125 inches (3 mm) and a total thickness of 0.25 inches (6.4 mm).  The Aluminum marker has the same physical characteristics but is designed and approved by regulatory authorities for activity content up to 0.6 mCi (22.2 MBq) of Na-22 or Ge-68.