Continue to Tone, Shape and Strengthen Your Abs With Your U-slender and This Conductive Gel! A breakthrough in fitness products. U-Slender uses the latest muscle flex technology to strengthen, tone, firm, shape and tighten your core. Simply use this conductive gel on the main unit (Item No. 62177), put it on the area you select, push a button and the advanced electronics begin emitting gentle electric impulses that cause muscles to contract and relax.