The eGo Twist has
thread on the inside and outside. The outside threads are eGo threads and the inside thread are 510 threads. A LOT of
tanks fit once you realize that - assuming you didn't already. Now if you did already know that, first I apologize, but second, maybe you got a defective one and should contact the seller. I use M3 clearos, ViVi Novas, U-DCTs, etc on both a Twist and a Vmax. Heck, even my Spitfire fits on the Twist.
Good luck and here's some pics....
1ml M3, 3ml U-DCT, eGo A Type Sleeve, eGo D Type Sleeve
eGo Twist, eGo A Type Sleeve, 1ml M3
eGo Twist, eGo D Type Sleeve, 3ml U-DCT
Sigelei ZMax Mod, 1ml M3
Blurry Sigelei ZMax Mod, 3ml U-DCT
Sigelei ZMax Mod, 2.5ml ViVi Nova (reference)