These are STANDARD 2.54mm pitch JST XH connectors that fit standard perfboards and standard PCB boards. Nearly all electronics I have ever used require 2.54mm pitch connectors: Ard...

These are STANDARD 2.54mm pitch JST XH connectors that fit standard perfboards and standard PCB boards. Nearly all electronics I have ever used require 2.54mm pitch connectors: Arduino micro controllers, LEDs, transistors, perfboards, PCB boards, breadboards, etc. Note that a few reviewers are confusing these with other types of JST connectors not designed for perfboards and rated these poorly based on their misunderstanding of what these are. There are dozens of different JST connector types. This set is just one subset of standard JST connector types. Read the specs carefully so you are sure this is the correct JST set for your needs.

This is a nice set. It's very useful.

Standard shipping from China to California took 18 days.

The parts box I received is not the same as the one pictured in the ad, which is a two-sided compartment parts box. The one I received looks a bit larger with adjustable compartments and it only opens on one side.

I read a few reviewers stating incorrectly that 2.54mm was not the "correct" pitch for JST XH connectors, and that 2.5mm was. This is simply false information. After getting the set I immediately tested all the connector sizes in this set to connect with motherboard connectors, battery connectors, 2-pin fan connectors, 4 pin connectors on 3D printers, all sorts of electronics, and found that everything I need JST XH connectors for is using 2.54mm pitch JST XH connectors. This is the most common size in use.

Most people will need 2.54mm pitch connectors, especially if using standard perfboards, PCB boards, or wanting to insert LEDs into these, because the standard in use for such electronic components is 2.54mm pitch and not 2.5mm pitch.

There are some 2.5mm pitch connectors out there, but none of the electronics I have ever seen use that size pitch. A 4 pin JST XH connector that's a 2.5mm pitch connector will be 0.16mm smaller from the left pin to the right pin than a 2.54mm pitch connector would be. They will fit each other, but the fit will be slightly tighter than it should be. But it will work fine. As the sizes get much larger than 4 pins, at 6 pins and up then the size difference will become a problem if you mix them up.

There are apparently thousands of products that use 2.54mm pitch connectors and some also use 2.5mm pitch connectors. Many JST XH distributors sell both options. This is an unfortunate thing, but such is reality. For the 4 pin or smaller connectors in this set, this is not an issue to worry because you can mix them up and they still work, because at most they can only be off by up to 0.16mm, which is not large enough to cause connection problems. The female sockets have enough play in them to allow up to 5 pin connectors to interconnect from either standard size.

The whole reason 2.54mm pitch connectors are in widespread use is because 2.54mm is equal to 0.1 inch, the standard grid spacing on many perfboards, breadboards, PCB boards, LEDs, etc., which is an inch friendly size, while 2.5mm doesn't work well with inches or most perfboards, breadboards, LEDs, etc., coming out to be 0.0984252 inches. Inches are still in use, despite the metric system being a better system. For those engineers designing in inches using perfboards and breadboards, LEDs, etc., the 2.54mm size is preferred over the 2.5mm pitch size. For those using the metric system then 2.5mm is preferred.

Since these connectors are up to 4 pins only they are also completely compatible with 2.5mm pitch connectors, so there's no worry about the pitch size. With 6 pins, you'll need to worry about matching, but with 5 pins or less, no worries.

All I care about is that these connectors fit what I need them to fit, and they certainly do! The quality is also good. So I am a happy buyer.