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Why is a socket’s length important?

Why is a socket’s length important?

What are the different socket lengths

As well as the size of a socket being determined by the head and drive socket sizes, there is also the length of the socket to consider. Most manufacturers will make sockets in two sizes: a ‘standard’ or ‘shallow’ size, and a ‘deep’ or ‘long’ size.The size of standard or deep sockets is normally determined by the standards to which they are made e.g. DIN, ISO etc.

Standard Sockets

Socket set including deep and standard sockets

Standard sockets allow access to fasteners that may be in areas that are obstructed by other objects. Deep sockets are useful for gaining access to fasteners in recessed cylinders, and long fasteners that extend up or down into the socket (such as the bolts on a car exhaust clamp).

Deep Sockets

Situation where a deep socket is required

 Deep sockets are often included in socket sets that contain a larger range of pieces (for more detail see: How to choose a socket set?), but it’s not uncommon for there to be a smaller number of deep socket sizes than standard socket sizes included in the set.


If bought separately, deep sockets will cost more than standard sockets, due to the increased material used to make them, and the lower production volumes of deep sockets.

Standards of Socket Sets

Comparison of deep sockets and standard sockets

There are many different standards for sockets and whilst they are generally similar, they may set different tolerances, giving an acceptable range of lengths within the same standard. This means one manufacturer’s deep 13mm socket may be slightly longer or shorter than another’s. 

Deep socket, mid length socket and standard socket

 It’s also possible to purchase ‘mid-length’ or ‘semi-deep’ sockets from some manufacturers. In some cases, these can be nearly as long as a ‘deep’ socket but they can fit in spaces that are often too tight for a deep socket, while still allowing access to a fastener that cannot be reached by a standard socket. These are not normally sold as part of a complete socket set, and are more expensive to buy than either standard or deep sockets.

Where can these sizes be found?

Manufacturer Product Description

While the main sizes of a socket, head size, drive size and length (although this may be given as simply standard or deep) are usually included in the description advertising the socket, many other sizes may not be. These should be included in the product specification or data sheet for the socket.

Online information on sockets

You should be able to obtain a copy of the product specification or data sheet from the retailer or they can often be found on the socket manufacturer’s website.

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