Does the choice of observation instrument make a difference in the feedback and ratings that teachers receive? This study explores how lessons are rated differentially across various observation instruments. To investigate this question, ten randomly selected mathematics lessons were rated using six different observation instruments. Overall scores varied little across instruments. Our analyses indicate that differences in scores can be attributed to what we call instrumental occlusion, instrumental emphasis, and element density. This article concludes with implications for the selection and use of observation instruments in school settings.