A quick attach spring retainer holds an extensometer arm onto a test specimen under a resilient load using a unitary spring that is quickly placed onto an extensometer, and which has low mass to minimize any effects on dynamic testing. The spring force is reacted so that it creates a very low disturbing moment on the specimen and extensometer in that this clamping force is applied directly diametrically across from the specimen engaging edge of the extensometer. The unit is made so that it is very stable by providing a three point contact with the spring and the specimen engaging edge. The attachment clip or spring is adjustable across a range of different specimen sizes, using the same type of fixtures, and is made to be a self contained assembly that is not easily lost or misplaced because there are no loose parts. The spring that is utilized is retained in a mounting bracket that is used for attachment.