Bought for the conversion of a small house with this renewal of the electrical drill bit. The walls vary in our old between butter soft and extremely hard stones. To use the Borhkrone came to Hilti rotary hammers and Makita and has consistently good drilled. The only drawback is that now (after about 150 holes) missing a tooth, holes makes Borhkrone but still wonderful. Would she so Recommend unreservedly.