UHV-EL 6 Rectangular Retainer, 9 x 12mm, with 6 reference standards (select from list)

UHV-EL 9 Square Retainer, 13 x 12mm, with 9 reference standards (select from list)

UHV-EL 12 Rectangular Retainer, 17 x 12mm, with 12 reference standards (select from list)

UHV-EL 15 Rectangular Retainer, 21 x 12mm, with 15 reference standards (select from list)

UHV-EL 18 Rectangular Retainer, 25 x 12mm, with 18 reference standards (select from list)

UHV-EL 37 Round Retainer, 25mm diameter, with 37 reference standards (select from list)

UHV-EL 37 Round Retainer, 25mm diameter, Standard Configuration with 37 reference standards