Now that I have invested much into experimenting with vaporizers and concentrates I highly recommend an eGo C Twist battery and iClear16 clearomizer (oil tank). Or go for a larger much more advanced vaporizer, the innokin SVD with the iClear30 attachment (oil tank). These devices are superior compared to all the other vaporizers I have tried.

SVD with i30 left, eGo C Twist with i16 right.
Attachment 295672

Both of these devices offer variable voltage which allows you to either turn the heat up or down. This makes a big difference. Also, the i16 and i30 attachments are rebuildable and they have dual heating coils instead of just one. I have found dual coils are much better for oil, especially for concentrates.