Loading... Please wait...7 pin "septar" ceramic plate style -3C33, 3E29, 4-65A, 826, 829B, 832A, 4D32, 5894, 7094, etc. -bottom mount with 1-7/8" x 1-7/8" square, 2.65" diagonal mounting centers. Chassis hole diameter depends on specific application and tube type used.