- O.B. tampons have Fluid-Lock grooves for locked-in protection you can trust. And they were designed by a woman gynecologist to custom-fit your shape perfectly. - Regular: Use For 8 Hours Maximum. Read And Save Enclosed Information For Complete Instructions. 1. Use The String To Flare And Enlarge The Base Of The Tampon. 2. Place Index Finger In This Newly Created Indentation.