HiFiMAN's new retail boxes are sturdy and protect the earphones well during transport. You can read about the main features of the new RE-400s on the front. Its main feature is the brand new 8.5 mm driver, of course.
The bundle for HiFiMAN in-ears has changed with the RE-400 earphones. You only get two double flange tips and one small single flange tip. The tip design is also brand new, with the two flanges being very close. This is something I have not seen on any other in-ear, and it works really well for the HiFiMAN design.
The mini-jack is not so mini and is identical to those featured on the RE-2x2 series in-ears. A smaller jack is nice from an aesthetical point-of-view, but the big and bulky might fare better in the long run, since they are more durable.
The design of the RE-400s looks sweet. Its bell-like shaped housings and the new tips look much better than the more ordinary design of the RE-0s, which the RE-400s supersede. The strain reliefs on the housing are still very large compared to what is featured on competing products; however, HiFiMAN's implementation works better than on most due to them being angled outwards slightly. Also, part of the bundle is a wire wrapper that is alright, but it is quite bulky.
HiFiMAN seems to be well aware of the huge potential optimized cable solutions have, and the new RE-x00 series in-ears feature a hybrid cable design. The cable is, from the y-split up, completely PU covered and features a braided sleeve from the jack to the y-split, which should make it withstand more physical abuse. This is quite a neat feature, since it effectively beefs up the cable where it needs reinforcement while retaining optimum flexibility and microphonics dampening around the most critical area.
The new tips are pretty different from what HiFiMAN used to make. The new fit kit only consists of three tips ranging from small through medium to very large. The medium-sized double flange will be killer for anyone that was able to get a good fit with the older medium single flanges. The small tips are much better than the old ones that were too sensitive to placement.