a) Sphere: made of brass, nickel plated, mounted on stand with metal tripod base, with a 5 cm wide opening at the top.
b) Conical: made of brass, nickel plated, 100 x 50 mm in size, mounted on insulated metal stand with tripod base.
c) Cylindrical: made of brass nickel plated 125 x 50 mm in size mounted on insulated metal stand with tripod base.
