Total number of items
The total number of items in the set. In this case, both the actual
bits and end heads are taken into account, as well as additional accessories such as an adapter, a bit holder, etc.
The more items in the set, the wider its possibilities. However, note that the specific composition of the kit may be different, so when buying it is worth specifying not only the number of items, but also their specific types.
Landing square
The size of the square of the bits / sockets supplied in the kit.
The seat square is a standard fixture used in bits and sockets. For installation on a bit holder, ratchet, etc., the size of the square must correspond to the size of the seat. However, complete fixtures (like the same bit holder) by definition have fasteners of the right size, so you have to pay attention to the size of the square mainly if you plan to use nozzles with third-party tools.
Also note that the overall dimensions of the complete bits / heads can be estimated from the landing square: the larger the square, the larger the nozzles. For example, in 1/2" sockets, the size starts from 8 – 10 mm, and in 1" sockets — from 24 mm.
Socket heads (E-profile)
The total number of E-profile sockets supplied in the set.
E-profile, also called
"external Torx" (E — "external"), has the shape of a characteristic six-beam asterisk. These sockets are used only with fasteners that also have an E-profile, they are not suitable for ordinary hexagons. Fasteners of this form are found mainly in cars.
