This is used on the .20 and .40 RC carburetor
and the later version of the front intake .61 4 bolt head, Also the rear intake 4 bolt head .61 that used had the bold on front and rear cover. It does not work on the early rear intake 4 bolt .61

This includes spray bar 84-2103 (with ratchet), spray bar nut 84-2104, and main needle 85-2101