Foren-Tests Semen Test Swabs are designed to provide the crime scene investigator with the ability to conduct a presumptive chemical field test for the presence of semen. Simply remove the protective cap, moisten the swab pad with the included water, rub the swab on the suspected biological stain to transfer a sample of the stain to the pad, break the crush vials in the plastic tube, and observe a color change in the swab pad to indicate a positive presumptive reaction to the presence of semen. Provided as a package of eight swabs.