The HI731225 are the replacement caps that screw on the glass cuvettes used with Checker HC colorimeters. The HI731225 includes 4 caps that are used with the HI731321 glass sample cuvettes. The HI731225 are the replacement caps that screw on the glass cuvettes used with the HI7XX Checker HC colorimeters. The HI731225 includes 4 caps for the HI731321 glass cuvettes.