This test that tells you when to shock for sparkling crystal clear water! ShockChek is a rapid, easy way to check if you need to shock your pool or spa. Just dip a strip and match to color chart which indicates a simple “Shock” or “Okay” result. Shocking is a necessary maintenance step that keeps the water clear of harmful contaminants that can cause irritation and spread water-borne illnesses. Comes complete with multi-lingual instructions and 10 test strips.