Estes Blast-Off Model Rocket Engine Assortment Bulk Pack - 24 Total Engines - 6 of Each: A8-3, B6-4, C6-3, and C6-5 (1672)PLEASE NOTE: These are 18mm diameter engines. Please refer to the instructions that came with your rocket (or the rocket's product description) to determine engine compatibility. The Blast off Bulk Pack comes with an assortment of top selling model rocket engines (24 total), along with 30 starters, 24 starter plugs, and ~72 squares of recovery wadding 24 engines total, 4 different types. Includes: Six A8 3 Six B6 4 Six C6 3 Six C6 5 Bulk packs are