Abstract: An expansion anchor includes a bolt, a spacer sleeve, an expansible sleeve, an expanding member, and a collar where the collar is disposed between the expansible sleeve and the spacer sleeve. The bolt is insertable into the spacer sleeve, the collar, and expansible sleeve in sequence and a thread of the bolt at a leading end of the bolt is connected to the expanding member to draw the expanding member into the expansible sleeve and expand the expansible sleeve radially. The collar is formed by a first material with a first hardness and a second material with a second hardness where the first hardness is different from the second hardness.