I have the Hifiman HE400i's and i must say the ZMF Ori pads are the best earpads on the market for Hifiman cans, i have tried the following: Shitty velour HIFIMAN earpads, Focuspads (stock 400i earpads), Brainwavz HM5 Angled pleather, HM5 Angled Hybrids and finally Dekoni earpads.
Now I'm gonna describe my experience with each pair of earpads, Comfort, sound, fit (of the earpads on the headphones), construction quality and looks.
Hifiman velours: By far the worst of the bunch and the cheapest off course, i'd say there is no reason to buy one of these besides ripping the mounting ring off, the mounting rings costs the same so buying the earpads is better even tho they are shit, maybe they are good for emergency replacement pair
Comfort: stiff foam, like really stiff cheap foam, velour feels cheap and itchy 3/10
Sound: Loss of lower end, kinda boring to listen, a little brighter than stock. 5/10
Fit: as intended, they are made by Hifiman. 10/10
Construction Quality: Cheeeeap 1/10
Looks: They are ugly, they make the headphones look cheaper 4/10
Focupads: These are the stock pads, and to be honest they are very good, if i wasn't so courious a would probably didn't have to switch these, but hey modding and earpad rolling is part of the fun. They are barely angled and kinda shallow, i like deep and very angled ear pads but that's my preference after all.
Comfort: They feel good, they are hybrid so the part that touches your face has velour, and a good one this time, one gripe i have with them is that they are kinda shallow so the tip of your ears can touch the driver, another problem with these earpads is their earhole, it's round so your ears don't fit easily without touching the edges of the earhole which is kinda annoying. 7/10
Sound: Sound as intended i guess, this is the base sound and i like it, the other earpads improve overall certain areas, with these earpads i think they sound the flatter, but soundstage is the smallest too. 8/10
Fit: Perfect 10/10
Construction quality: very good overall i have no complains, good quality pleather and velour, stitching is nice. 9/10
Looks: They look nice but they look small on the headphones, i like big earpads but that's subjective and you may like the opposite. 7/10
Brainwavz HM5 Angled pleather: These are a very popular option among Hifiman users, they feel nice and pricing is good they are very angled as i like but they have some flaws.
Comfort: They feel nice, earhole is oval but quite tiny there is a chance your ears will touch the edges of the earhole, they are full pleather so you may sweat a little in summer, they are made of memory foam so they are comfortable and plushy.
Sound: Improved bass and midbass, treble takes a hit, soundstage improved a little. 8/10
Fit: This is the weakest point of these earpads, they are oval earpads and Hifiman cans are round so you have to stretch them to fit, you should take your time stretching them or you may break the mounting ring, it is quite a pain in the ass to mount these earpads to be honest, once you mounted them they look weird, i mean fit is far from perfect some parts of the earpads will be stretched and they won't fill the cups entirely, other issue is clearance under the yokes it's a tight fit. 4/10
Construction Quality: One earpad is slightly bigger and more angled than the other, not a big deal, overall they are well constructed. 8/10
Looks: As i said before they don't fit right on the headphones so they obviously don't look that good, if you are not too picky they are fine but i'm very ocd with these kind of things. 7/10
Brainwavz HM5 Angled Hybrids: Well they are exactly the same earpads, the difference is these have velour on the inner part of the earhole and in the part that makes contact with your face.
Comfort: the same as the pleathers but a little different because of the velour they can be better for hot weather but velour can get a little itchy.
Sound: Treble goes away even more, there is not a huge difference but to my taste i would stick to the pleathers if you want HM5's, 7/10
Fit: Same as HM5's pleathers. 4/10
Construction quality: Same as above. 8/10
Dekoni sheepskin: Very good earpads overall, i have heard some issues with them and Fostex headphones, but they work fine on the HE400i.
Comfort: Glorious memory foam, earholes should be a little bigger but still they are better than the ones on the HM5's, sheepskin is smooth and very thin. 9/10
Sound: Good overall, improved bass, mids are almost untouched high end is controlled but they miss some of the glare nothing dramatic tho, soundstage is slightly bigger.
Fit: they fit all right.
Construction quality: sheepskin feels great, memory foam is very nice, but they have some irregularities on the stitching (these can be a particular case tho, maybe yours are perfect)
Looks: they look very nice and headphones look premium but stitching could be better.
ZMF Ori earpads: best quality of the pack, but packaging is ugly just a plain brown box, they should improve in that area these are quite expensive earpads, they are angled maybe a little more than the Dekoni but not as much as the HM5's i think size is perfect, yokes can rotate freely to a certain point, clearance is about right and they wont cause any issue under normal use.
Comfort: As good as the Dekoni pads but a little better, earhole is oval and the bigger of all i the earpads i have tested, they fit tremendously well in my ears, these are the most comfortable hands down.
Sound: they more or less improve the sound on every area, Bass is much better, mids clear and treble detailed and controlled (i'm a treble head so this is important.) Soundstage is improved too, (i did remove the fabric on the inside of the Ori's to have more of those juicy highs.)
Fit: like a glove, very easy to install.
Construction quality: Materials are great, excellent quality all around, stitching is consistent and both earpads are the same size (looking at you HM5's).
Looks: they look amazing on the headphones they feel more premium with the Ori's installed.
This is all just my opinion, and some issues can be isolated cases like stitching on the Dekonis and irregular sizes on the HM5's (even tho the pleathers and the hybrids present the same issue)