The WILDERNESS BUTTON HEAD BOLT is a compression type bolt that is essentially "forced" into the hole thereby exerting pressure along it's offset "wings" - which create the holding power. It is appropriate for high quality, hard rock - like granite - when drilling time and bits are at a premium. The strength of this type and size bolt is similar to an optimally placed piece of trad gear - use consciously on back country, alpine and expedition first ascents. Care is needed to maintain the diameter of the hole while drilling an oversized 5/16" hole - as well as carefully starting to pound in the bolt to avoid fracturing or "spawling" the rock.