The ATP1S 360 deg. prism is exclusively designed for the PR4 pin pole system. The prism slides along the pin pole, The HI can quickly be adjusted from 4 in. to 15.7 in. The lower prism height makes it easier to achieve highly accurate measurement by reducing error from wobbling poles. The prism is equipped with a built-in circular level to ensure the highest precision in all surveying and engineering and construction applications, specifically in stake-out measurement. The Sokkia 360 prisms and SRX Auto targeting are rated the industries best for accuracy.