Astro Tools Half Size Sockets for Rounded and Swollen Bolts

Best for
Swollen lug nuts on tight wheels

The Astro Tools 78204 4-Piece 1 2″ drive set is the lug nut specialist. It includes four half size, thin wall impact sockets in 17.5, 19.5, 21.5 and 22.5mm, aimed squarely at damaged, swollen and stuck lug nuts. Swollen lug nuts are a common headache on vehicles that use two-piece nuts with a decorative cap, because the cap can bulge until a standard socket will not seat. A half size up is often the only way to get a grip without destroying the nut further.

The thin wall design is the other reason to choose it. Many alloy wheels have narrow lug holes, and a chunky impact socket simply will not drop in. Astro says this set is built for tight-access lug nuts and wheel designs where space is limited. The listing gives a weight of 2.5 pounds for the set.

This is the set to keep with your tire tools. It is not a general-purpose kit, so if your trouble is with bolts elsewhere on the car, the 78311 covers far more ground.

• Sizes: 17.5, 19.5, 21.5 and 22.5mm
• Thin wall for tight wheel pockets
• Impact rated

Best for
General rounded and swollen hardware

The Astro Tools 78311 11-Piece 3 8″ drive set is the core of the half size idea. It covers 9.5mm through 19.5mm in half-millimeter steps, which lands right in the range of most engine, suspension and body fasteners. Astro’s guidance is simple: go 0.5mm under for rounded and damaged heads, and 0.5mm over for swollen or corroded bolts and capped nuts.

The listing says the sockets work with hand tools and impact wrenches, and it suggests using a hammer to seat an undersized socket on a rounded head when needed. That is a well-established trick: driving the socket on gives it a bite on the remaining flats. Astro also notes the set works on worn SAE fasteners by stepping down the effective hex size, so it earns its place in a mixed-standard garage. The set weighs 16 ounces according to the listing.

If you only buy one half size set, this is it. The one limit is profile: it uses regular socket bodies, so for jammed-in spots the Nano version below may fit where this one cannot.

• 11 sockets from 9.5 to 19.5mm
• For rounded, swollen, corroded and capped hardware
• Hand tool and impact use
• Helps on worn SAE fasteners

Best for
Rounded bolts in cramped engine bays

The Astro Tools 78312 3 8″ Drive half size Nano set takes the 78311 idea and moves it into Astro’s low-profile Nano family. Each socket has a 3/8″ square drive plus a 17mm outside hex. That hex means you can turn the socket with an ordinary 17mm wrench when there is no room for a ratchet, or retain it in Astro’s 78318 and 783105 Nano socket ratchet wrenches.

The same half size guidance applies: under for rounded, over for swollen. The sockets are forged Cro-Mo, and the warranty process is to send Astro a photo of the broken tool with your address to receive a replacement. The listing does not specify the piece count or the exact size range, so check the product image or confirm with the seller if you need a specific size.

Pick this set if your rounded bolts tend to sit in tight engine bays or behind brackets. If you work in open spaces, the 78311 does the same job with a known size range.

• 3/8″ drive with 17mm outside hex
• Works with a standard 17mm wrench
• Forged Cro-Mo
• Photo-based warranty replacement

Best for
Driveshaft and U-joint bolt work

The Astro Tools 78250 1 2″ Drive set is not a half size set, and it solves a different access problem. It holds 12-point impact sockets for driveline bolt heads in the common driveshaft sizes of 1/2″, 3/8″, 12, 13 and 18mm, covering domestic, import and heavy-duty applications.

Two design details stand out. The pinless universal joint gives a full 360 degrees of freedom to angle and rotate, which helps when the driveshaft flange sits at an awkward angle to your impact wrench. And Astro’s “torque-saver” extension design is said to transmit more of your impact’s output to the fastener, so a smaller class of impact can still do the job. If you already use Astro’s wobble sockets for angled access, this set pushes the same idea further for driveline work.

Buy it if you pull driveshafts. It is not the answer to rounded or swollen hardware, so pair it with a half size set rather than choosing between them.

• 12-point sockets for driveline bolts
• Sizes 1/2″, 3/8″, 12, 13 and 18mm
• Pinless universal with 360 degree movement

Best for
Low clearance full-size lug work

The Astro Tools 78214 14pc 1 2″ drive set covers 17mm to 30mm with no skipped sizes, in low-profile Nano impact sockets. Astro says they are 75% shorter than standard shallow impact sockets of the same range, which matters on axle nuts, suspension bolts and anywhere a regular impact socket leaves no room for the tool.

Each socket carries a 22mm outside hex, so any 22mm open end, box end or ratcheting wrench can turn it. Astro pairs it with its 78218 18″ ratcheting wrench, which retains the sockets. The sockets are forged Cro-Mo, and the lifetime warranty works by emailing Astro a picture of the damaged socket.

These are standard whole metric sizes, not half sizes, so they do not solve a swollen lug nut on their own. They suit mechanics who need clearance first and already own a half size set for damaged hardware.

• 17 to 30mm with no gaps
• 75% shorter than standard shallow impacts
• 22mm outside hex for wrench use
• Lifetime warranty by photo

Best for
Small metric fasteners in tight spots

The Astro Tools 78113 13-Piece 1 4″ drive set brings the Nano low-profile design to small metric fasteners. The listing is thin: it confirms 13 metric pieces, a 1/4″ drive, impact use, a weight of 8.48 ounces and manufacture in Taiwan. It does not specify the size range, the outside hex size or the warranty terms.

Based on what the listing does confirm, it suits interior trim, sensor mounts and small brackets where a standard 1/4″ socket and ratchet stack is too tall. Check the size range before ordering if you need a particular fastener covered. Sorting a set like this is easier with a clear home for loose hardware too; some builders keep bolts in half-gallon wide-mouth jars on the shelf above the bench.

• 13 metric sockets
• 1/4″ drive, low profile, impact rated
• Weighs 8.48 ounces