The Klein 646-5/16M is a single hollow-shaft nut driver measuring 9.75 x 2 x 2 inches and weighing 0.2 pounds, priced at $11.99 with a 4.8-star rating from 738 reviews and 100 monthly buyers.
Electricians and service technicians who need a 5/16-inch hollow-shaft nut driver for accessing long fasteners at a budget-friendly price within the Klein lineup.
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Buyers who only work with short fasteners where a compact solid-shaft driver would be sufficient, or those who need a different drive size.
Weight 0.2 Pounds
Dimensions 9.75 x 2 x 2 inches
Pieces 1
Priced 25% below the category median ($15.99 across 47 tracked models)
Our scorecard
4.7/5overall
Owner rating4.8/5
4.8 average across 738 owner ratings
Popularity1.8/5
738 owner reviews, fewer than most models here
The overall score is owner satisfaction weighted by how many reviews back it, so a high rating from few reviews counts for less. The bars below show where this model stands against the other hand tools and workshop hand tools we track in this category on price, popularity and size. Context, not marks against it, and our read of the data, not a lab test.
Overview
At $11.99, the Klein 646-5/16M delivers hollow-shaft nut driver access at one of the lowest prices in the Klein range. The 9.75 x 2 x 2-inch footprint and 0.2-pound weight confirm a full-length tool that does not sacrifice reach, while the hollow-shaft design handles fasteners that extend beyond the nut without bottoming out.
The 4.8-star rating from 738 reviews and 100 buyers per month provide a strong quality signal for a specialized single-size tool. Hollow-shaft nut drivers are a staple in electrical work, and the 5/16M designation targets a specific metric-adjacent size common in panel and conduit applications.
For the $11.99 price, buyers get Klein's engineering in a hollow-shaft configuration that would otherwise require spending more on broader sets. The 0.2-pound weight keeps it easy to handle throughout a workday, and the 9.75-inch length provides the leverage and reach that professionals expect from a hollow-shaft driver.
Pros
4.8-star rating from 738 reviews confirms consistent quality at $11.99
Hollow-shaft design at full length (9.75 inches) for deep fastener access
0.2 pounds is light for a full-length hollow-shaft tool
100 monthly buyers shows steady professional demand
One of the most affordable hollow-shaft drivers in the Klein lineup
Cons
Single size limits versatility for multi-size applications
9.75-inch length can be unwieldy in confined or tight spaces
Hollow-shaft capacity is not specified in the listing data
Specifications
Weight
0.2 Pounds
Dimensions
9.75 x 2 x 2 inches
Pieces
1
Performance notes
The Klein 646-5/16M measures 9.75 x 2 x 2 inches and weighs 0.2 pounds, making it noticeably lighter than the 646M (0.42 lbs) despite similar length. The hollow shaft allows the tool to pass over threaded rods and long fasteners without the shaft base contacting the work surface. The 4.8-star average from 738 reviews supports reliable performance in electrical and HVAC fastening tasks.
What buyers say
Owners consistently praise the Klein 646-5/16M as a solid hollow-shaft option at a price that does not require significant budget allocation. Professional users note it as an easy add-on for specific size coverage in trade tool kits. Few complaints are recorded across the 738 reviews.
What is the hollow-shaft capacity of the Klein 646-5/16M?
The listing does not publish a hollow-shaft depth for this model. For the 646M variant, a 6-inch capacity is listed. Contact Klein or the seller to confirm the 646-5/16M specification.
How does the Klein 646-5/16M differ from the Klein 610-5/16?
Based on available listing data, the 646-5/16M measures 9.75 x 2 x 2 inches and weighs 0.2 lbs at $11.99, versus the 610-5/16 at 0.1 lbs and $7.99. The 646 series is associated with hollow-shaft designs in the Klein lineup, while the 610 series is a more compact solid-shaft option.
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