Rocketry Starter Sets & Engines > Estes 13mm Mini   Estes 1/2A3-2T 13mm (4-pak) model rocket engine Single stage engine (green label) $ 6.75          Available: 3      More Information      Quantity:     Estes 1/2A3-4T 13mm (4-pak) model rocket engine Upper stage engine (purple label) - can also be used as a single stage engine. $ 6.75          Available: 3      More Information      Quantity:     Estes 1/4A3-3T 13mm (4-pak) model rocket engine Single stage engine (green label) $ 6.75          Available: 3      More Information      Quantity:     Estes A10-3T 13mm (4-pak) model rocket engine Single stage engine (green label) $ 6.75          Out of Stock      More Information Estes A3-4T 13mm (4-pak) model rocket engine Single stage engine (green label) $ 6.75          Available: 1      More Information      Quantity:     Estes Mini to Standard Engine Adpaters (3) Two simple steps transform a 13mm mini engine into a 18mm standard size. Insert a mini engine into the Estes engine adapter, and insert the adapter into a rocket. 3 adapters per pack. Reusable. $ 4.75          Available: 2      More Information      Quantity: