Markbass rack ear kits (with screws included) come in four sizes: Standard, Little Mark, F Series and MoMark. Little Mark rack ears are not included with Little Mark and LMK heads. F Series rack ears are not included with the purchase of an F1 or F 500. MoMark rack ears are not included with MoMark Amp Frames. Standard rack ears ARE included with the following heads, but also available for separate purchase: SA 450, SD 800, SD 1200, TA 501, TA 503, R 500, TSA 500, Studio Pre, Studio Pre 500.