I love my ipv4s!!♡♡ incredible battery life! upgradable firmware, easy access no screw battery back, runs kanthal, titanium, and nickle wire. fires down to .1 sub ohm. nice display, great price, feels great in hand. works perfectly. has the new Yihi chip, no issues whatsoever.also 120 watts. memory to your favorite settings. I have had the ipv, ipv2, ipv3,and now the ipv4S and I NEVER had ANY problems with ANY of them. in fact I used them until a new model came out I wanted. They are sturdy! I've dropped my ipv3 about 100 times and it never damaged the unit! the yihi chip that controlled the readings is ALWAYS spot on. I can HIGHLY RECOMMENDED the IPV4S!! It's been a wonderful unit! hope this helps. you won't regret getting the ipv4s. I know I dont.