Cast metal, For holding flat objects like manometer, board, etc. upto 34 mm. thick in the vertical position. Size 9.5 cm length and 7.5 cm width.
Cast metal, For holding flat objects up to 13 mm thick. Size 10.5 cm length and 8.5 cm width.
Plated spring steel wire with finger grip, with a wire collar to hold test tubes up to 38 mm.