Hotswap Sockets

There are many different types of models of hot stwap sockets. This is my attempt to centralize the information in a readable format.

Manufacturer Series Model # Shell Contact Lip Length Notes
Mill-Max 3305 3305-0-15-15-47-27-10-0 Gold Gold 0.10mm 2.67mm Loose
Mill-Max 3305 3305-0-15-80-47-27-10-0 Tin Matte Gold 0.10mm 2.67mm Loose
Mill-Max 3305 3305-1-15-15-47-27-10-0 Gold Gold 0.10mm 3.30mm Loose
Mill-Max 3305 3305-1-15-80-47-27-10-0 Tin Matte Gold 0.10mm 3.30mm Lose
Mill-Max 3305 3305-2-15-15-47-27-10-0 Gold Gold 0.10mm 3.94mm Loose
Mill-Max 3305 3305-2-15-80-47-27-10-0 Tin Matte Gold 0.10mm 3.94mm Loose
Mill-Max 3305 3305-2-57-15-47-27-10-0 Gold Gold 0.10mm 3.94mm Tape Reel
Mill-Max 3305 3305-2-57-80-47-27-10-0 Tin Matte Gold 0.10mm 3.94mm Tape Reel
Mill-Max 7305 7305-0-15-01-47-01-10-0 Tin Tin 0.14mm 2.67mm Loose
Mill-Max 7305 7305-0-15-01-47-27-10-0 Tin Gold 0.14mm 2.67mm Loose
Mill-Max 7305 7305-0-15-15-47-27-10-0 Gold Gold 0.14mm 2.67mm Loose
Mill-Max 7305 7305-0-15-80-47-27-10-0 Tin Matte Gold 0.14mm 2.67mm Loose
Mill-Max 7305 7305-0-57-15-47-27-10-0 Gold Gold 0.14mm 2.67mm Tape Reel
Mill-Max 7305 7305-0-57-80-47-27-10-0 Tin Matte Gold 0.14mm 2.67mm Tape Reel
Mill-Max 0305 0305-2-15-80-47-80-10-0 Tin Matte Tin Matte 0.25mm 3.94mm Loose
(There are 36 different model numbers for 0305 series sockets. There are not all written down here.)

Mill-Max explanation of model number:

Mill-Max 3305: 3305 - Receptacle | Mill-Max Mfg. Corp.

Mill-Max 7305: 7305 - Receptacle | Mill-Max Mfg. Corp.

Mill-Max 0305: 0305 - Receptacle | Mill-Max Mfg. Corp.

I would recommend the 3305 line in tin, if getting enough for 2 boards the bigger bulk distributers might make sense:

Edit: Original Post
A few months ago I added Holtite sockets to a Leopold FC980m. After some trial and error I stumbled across someone who had a one liner Reddit comment reply saying use solder paste. I ordered some on Amazon and it worked out great I was able to get all of the sockets flush with the PCB. No shenanigans with tinning the sockets and minimal filling sockets with traditional solder.

After at least 4 whole board switch swaps I only had a problem with one socket that was pulled out with a switch. I was able to resolder paste and install the socked quickly. (I think it came out because I was using switches that had been soldered before and didn’t have super clean pins.)

I did try some Mill-Max sockets (models: 7305 & 0305) but didn’t like how the lip of the sockets made the switches sit above the PCB. I couldn’t get one of the switches to sit flush against a plate in a numpad set up so I went the Holtite direction.

I am about to start doing this again on another board and I realized that Holtites fell out of popularity a while back. I am curious does anyone know why? (ie Mill-Max are just superior, Holtites are too hard to install and/or PCB compatibility is not good failures etc)

Is there any other alternative to Holtite or Mill-Max? (Kailh ones require being designed into the PCB so they aren’t an option for my case)


In my opinion Kailh sockets are hands down the best. There is one problem. The PCB has to support them, so unless you are building a board that has a PCB that supports them, you won’t be able to use them. As far as I know Holtites and Mill-Max are your only option.


Thanks for you feedback. I will stick with Holtites for this build.

My current technique is good but but I ordered some of those one key PCBs to see if I can turn it into a jig for under the PCB while soldering to keep the sockets super straight.

One thing I’d like to see PCB designers start doing is sizing their PCB pinholes to the 7305 spec size (1.524mm), which is a tiny bit bigger than the cherry MX spec footprint hole size. I switched my switch footprints to the larger size and 7305s sit lower on the PCB, install more cleanly and look nicer.


Oh do you have a pic of the switches sitting lower? I major complaint I’ve always heard is the switches sitting too high

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Unfortunately i don’t have any PCBs with 7305s installed that aren’t currently built into a keyboard. Next time i have something disassembled I’ll snap some shots…I can’t say for certain that it changes how the switches sit, I just noticed a clear improvement in how the sockets sit when installing the 7305s. Maybe i’ll pop some sockets into a spare PCB tonight and see if I can tell a difference on how the switch sits.


Had some extra Mill-Max sockets lying around so Dremmeled one down to be as thin as possible while still having a lip. This is really hard to see in person let alone in a picture. But even the dremeled one sits just off the PCB. Maybe I could create a 3d printed part to fit under the switch like a switch film but that seems like way more work then I want to get into right now.

I would love to see if PCBs could be made to better handle these sockets with a stepped holes or ones that are at an angle to better handle these. I want to like the Mill-Max more they are easier to install, look more durable but I am still a fan of that flush install of the Holtites

Photo sockets:

  1. Mill-Max 7305
  2. Mill-Max 0305
  3. Mill-Max 0305 ground down
  4. Switch is just sitting in the PCB

Mill-Max Socket close up. (The one I Dremmeled in the photo was an oopsie but in reality it is about 1/2 the lip height of the 7305.


I can totally see it in the photo - the un-modified ones don’t let the little corner nubs touch the PCB.

I’m really glad I found this out before I soldered a bunch of those in, because I did just get some Milmax sockets - though reading through this thread and checking back through my keeb modding playlist I realized it was Holtite sockets that I meant to get. This guy makes installing them look pretty easy:

At least it’s not a wash - I’ve got plenty of abrasive dodads to experiment with…


That is a good video! It varies greatly from PCB to PCB. Some are very tight and it is a squeaky to push it to the right spot, others are super loose. If it is loose you can apply a little bit of solder then suck it out and it slightly reduce the diameter of the hole, holding the socket tighter (or you can try solder paste, which I am still experimenting with).

Regardless of the technique, it is extremely satisfying to get the sockets flush. Good luck!

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Bumping this thread to ask if anyone knows a decent source for Holtite sockets. So far the cheapest I’ve found them in the US is ~25 cents apiece for the quantity I’m looking for:

I normally do DigiKey around $0.22 for 250 (but they are out of stock)

Online Components? (Never heard of them but they are $0.165 ea + $8.99 shipping)


Fantastic - thank you!

Just placed an order with Online Components that’s supposed to ship tomorrow. If you see a big pile of them in an upcoming mail-day post you’ll know they’re legit. :stuck_out_tongue:


Bumping this post because I added all the new Mill-Max socket models to the first post post.Hotswap Sockets

This is also a great video explaining how to install the sockets and comparing some of them.


I was talking with someone who was using the new Mill-Max sockets that were siting higher then my previous photo with the same sockets. This was because the Boba switches have a nice tiny indents on the bottom that the sockets sit in making them slightly lower. (other switches may have this to but the cherry, zeal and misc other switches I had on hand did not)

This album show the differences between Cherry and Boba switches with different socket types.


Some new Kailh hotswap sockets are out in different colors and different contact material, they have upped the switch insertions to 6,000 from 100. Black never bothered me but I can see white being interesting to change things up.

Edit: I knew I had seen the image somewhere: Keyboard Builders' Digest - #45 by dovenyi


Yeah, it was featured three weeks ago. These sockets appeared in their store but with 60 million hotswaps cycles indicated. :wink: And four days later they modified it to the more humble 6000:


New Kailh hotswap colored sockets. The jade green ones have an odd color (not sure what I am going to use them for). Cream ones are nice. Might pair up with a white PCB


That “jade” reminds me of that stuff they call wasabi in gas station sushi packs.

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TaekayKeyboards’s gonna start painting these soon, mark my words.

Maybe lol. They can probably be custom dyed them if someone is really going for a special look. I did that with some JST connectors for a friend it took like an hour and a half on the stove for the color to set in but they came out nice. I don’t know if it is worth the trouble unless it is a super see through case.

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