Nepros NBR390A, a 90-tooth Ratchet Whose Design Has Evolved From Innovation to Superiority
Written by Luis Montes Updated On April 8, 2026
The Nepros NBR390A is the upgraded version of the already high-quality 90-tooth 3/8" drive ratchet from KTC (Kyoto Tool Company) top-tier tools line.
The profile of this mirror-polished chrome ratchet has become slimmer, allowing you to work in really tight spaces. However, the smaller size isn’t associated with reduced functionality or strength.
In this post, we’ll cover what’s changed compared to the last iteration, how the Nepros NBR390A compares to other compact ratchets, and discuss a few misconceptions we’ve seen on the web.
A Reduced Profile and Weight With the Same Strength
Photo source: https://www.youtube.com/@t.sawayama.
At a glance, one can immediately notice the difference in head size between the old NBR390 and the new NBR390A.
Photo source: https://www.youtube.com/@mono-story.
The NBR390A head had been reduced all around without changing the tool length, resulting in a longer neck. However, the most evident change is the head width, from 30 mm to 26 mm.
Internally, there have been a few changes as well.
First, the handle hollow section on the NBR390A is even longer, reducing weight and making this ratchet an extremely well-balanced hand tool.
Photo source: https://www.youtube.com/@t.sawayama.
Photo source: https://www.youtube.com/@mono-story.
Second, the ratcheting mechanism has been redesigned to fit the smaller head size without dropping performance. As you can see in the image below, the switch selector is completely round and integrated with the lever, and although the pawl is narrower, it engages the gear with 8 teeth instead of 7.
Photo source: https://www.youtube.com/@mono-story.
Besides being smaller, the new drive gear has a round machining groove on each side, which, along with the longer, hollow handle section, reduces the overall weight of this ratchet by 10% compared to the older version (275 grs → 245 grs).
Comparison Between Similar Models
The table below compares the Nepros NBR390A to similar top-tier compact ratchets from other brands.
Something worth mentioning is that Nepros is below average in size among compact ratchets, and its back drag is also among the lowest, slightly beaten by the 3725Z Ko-ken Z-series ratchet from another Japanese high-quality tool manufacturer. If you’re curious, we have an article focused entirely on Ko-ken's Z-series ratches.
| Brand | Model | Toot Count |
Length / L (inches) |
Head Width / B (inches) |
Head THK / T (inches) |
Weight (pounds) |
Back Drag (grams) |
|---|---|---|---|---|---|---|---|
 |
NBR390A | 90 | 7 | 1 | 0.5 | 0.54 | 277 |
|
3725Z | 72 | 7 | 1.1 | 0.5 | 0.52 | 224 |
|
CR38 | 72 | 8.5 | 1.2 | 0.5 | 0.98 | 293 |
|
435SG-QR N | 80 | 7.6 | 1.2 | 0.6 | 0.60 | 718 |
|
8816 HP | 90 | 7.9 | 1.3 | 0.6 | 0.57 | 456 |
Misconceptions About the NBR390A Drive Gear
The grooves on the drive gear has lead to some misconceptions. Let’s break down two of them.
The Grooves Are Not for O-rings
According to KTC’s flyer for the NBR390A ratchet, the purpose of the drive gear grooves is to reduce the ratchet’s weight and disperse inner stresses.
We’ve seen guys who think the grooves are meant for o-rings and have even recorded themselves fitting their NBR390A ratchet with them, which doesn’t make any sense, since it doesn't seal anything and goes against the intended purpose of the grooves, even with the o-ring's weight.
The Back Drag Hasn’t Changed
Photo source: www.youtube.com/@mono-story.
Because of the structural differences, the ratcheting on the NBR390A sounds louder than the previous version. For that reason, some YouTubers claim that the NBR390A's back drag is greater.
However, the Japanese YouTuber @t.sawayama confirmed with KTC that the back drag hasn’t changed, and @mono-story, another Japanese YouTuber, tested the back drag of the NBR390 and NBR390A versions with an FTD5CN-S Dial Torque Driver and proved they are both 0.03 N-m (0.27 lb-in).
Last Thoughts
The Nepros NBR390A has become even smaller than its predecessor, while retaining its low back drag, upgrading the pawl from 7 to 8 steps, making the switch selector more ergonomic, and maintaining its chrome finish, mirror-polished as ever.
If you’ve never used these ratchets before, this is the one you should start with. Don’t let its stylish look deceive you; this ratchet stands up to professional abuse. As this member of Reddit says, “Nepros isn’t some safe queen brand; they make their stuff for Industrial use. It’s a hand tool that you’ll use for life, and your kids will do it too.”
KTC has applied the same thought process they used for their ratchets to their wood handle screwdrivers. Check out our article “Nepros Wood Handle Screwdrives, High Quality Tools Wrapped in a Gorgeous Vintage Design” for detailed information on these gorgeous hand tools.