Though not the best picture, these are the horizontal dropout disc brake adaptors that go below the chainstay. My friends used to tell me I was crazy for running them that way, like it was my choice!
The picture actually shows the bike mounted with v-brakes, but you can clearly see the caliper bosses and how the caliper would be quite below the chainstay.

March 15, 2017, 1:13 p.m. - David Álvarez
Though not the best picture, these are the horizontal dropout disc brake adaptors that go below the chainstay. My friends used to tell me I was crazy for running them that way, like it was my choice! The picture actually shows the bike mounted with v-brakes, but you can clearly see the caliper bosses and how the caliper would be quite below the chainstay. 