Product Overview
The 5/16 Impact Socket That Keeps Hold of the Fastener
Condition
Unused stock. One socket was taken out for the photos and shot on the bench against a millimeter rule and again in daylight, alongside a labeled bag from this stock. The body carries a struck-in factory number that reads 7210HF on one flat and the size 5/16 on another, and the finish is dark and non-reflective, photographing close to black under bench light and lighter gray in daylight. The six-point opening looks crisp with the magnet seated at the base of the bore, the 3/8 in square drive end is clean, and no rounding, chipping or corrosion is visible in these photos. Stock is five, so the photographed socket is representative of the group.
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Product Overview
The Proto 2MA48 is a 5/16 in magnetic impact socket on a 3/8 in square drive, and the bag label spells the whole specification out in shorthand: SKT 3/8DR HI STR MAG IMP 5/16, MADE IN USA. Proto's factory number for it is J7210HF, which is what the 7210HF struck into the body refers to; 2MA48 is the stock number printed on the same bag label, so both numbers find this socket. The opening is a six-point SAE profile, which loads the flats of a 5/16 in hex head rather than the corners, and a magnet sits at the base of the bore to hold the fastener in the socket while you line it up. Against the millimeter rule in the photos the body measures roughly 30 mm long, about 1-3/16 in. The original product data lists a black oxide finish; what the camera shows is a dark, non-reflective surface with the matte texture of an impact socket rather than the polish of a chrome hand socket. Torque and drive ratings are not confirmed here - verify against the manufacturer's data before use.
Key Features
- 3/8 in square drive
- 5/16 in opening, six-point SAE profile
- Magnet seated at the base of the bore, visible in the photos
- Impact socket, high strength, per the bag label reading SKT 3/8DR HI STR MAG IMP 5/16
- MADE IN USA printed on the bag label
- Proto factory number J7210HF, struck into the body as 7210HF
- Stock number 2MA48 printed on the bag label
- Dark, non-reflective finish as photographed; original product data lists black oxide
- Body measures approximately 30 mm long, about 1-3/16 in, against the millimeter rule
- Unused stock, sold each
Applications
- Fleet techs running 5/16 in hex head self-tappers with a 3/8 in impact wrench, where the magnet keeps the screw seated instead of on the shop floor
- Panel builders and electricians driving 5/16 in hex head sheet metal screws overhead, one-handed, with nowhere for a dropped fastener to land but inside the enclosure
- Maintenance shops replacing the one size that walked off out of an otherwise complete 3/8 in impact set
- Anyone building a dedicated impact rail for a machine that uses 5/16 in hex heads throughout
Frequently Asked Questions
What fastener does this fit?
A 5/16 in across-the-flats hex head, SAE. The six-point opening grips the six flats, which is the profile you want on an impact wrench where a twelve-point can start to round a tired head.
Why are there two part numbers?
J7210HF is Proto's factory number, and the socket itself is struck 7210HF on one flat. 2MA48 is the stock number printed on the bag label. Both refer to this same 3/8 in drive, 5/16 in magnetic impact socket.
Is it actually rated for an impact wrench?
The bag label reads SKT 3/8DR HI STR MAG IMP 5/16, so it is sold as a high strength impact socket rather than a chrome hand socket. Specific torque figures are not confirmed here - verify against the manufacturer's data before use.
What do I get for one order?
One socket. The bag label in the photos reads 1 Unit, and the photographed socket is representative of the five in stock rather than a specific reserved piece.
Why buy one or two of these instead of a whole impact set?
Because you are missing a 5/16, not a set. Buy the single socket the truck needs, or take three or four to restock a shop, and skip paying for nine sizes you already own twice over. There are five here, so pick your count. Shipping is a flat $8 on orders under $28 and free once the order passes $28, and orders leave our Idaho warehouse the same or next business day.
A 5/16 hex head dropped into an engine bay is gone until it decides otherwise, which is the entire argument for the magnet sitting in the bottom of this bore. Hang it on the rail where the missing size used to be and get back to work.
