General screening test for controlled substances. Designed as the starting point for sequential testing. If you have a totally unknown substance (tablet, capsule, powder or chunk), the Mayer’s Reagent will direct you toward your next field test. ODV 7601 NarcoTest Mayer’s Reagent (General Screening) odv7601Regular price: $19.99Sale price: $12.95 Copyright 2012 Police Supply Online providing Police Equipment to over 300 Police, Federal & Military Law Enforcement Agencies around the world.