Our Classic Insta Slim Shirts. The one's that started it all! Our Insta Slim Compression Muscle Tank, Crew Neck and V-Neck are great for slimming down and getting tone, INSTANTLY! Get rid of your lumps, bumps, and bulges and feel confident in any of our shirts. Whether it's a night out, working, or just at the gym; take Insta Slim with you everywhere you go and feel your best!