'A pair of...?'
A pair of is used with two things that look the same, are the same size and are meant to be used together.
Example:
A pair of shoes
A pair of pajamas
A pair of gloves
We also use a pair of for something that is made of two items joined together
Example:
A pair of glasses
A pair of scissors
A pair of trousers
Note: A pair of is always followed by a plural noun. E.g. 'A pair of gloves', NOT 'A pair of glove'.