24 Engine Blocks for Mini Engines. Fits BT-5 Tube.

24 Engine Blocks for Standard Engines. Fits BT-20 Tube. Engine Block or Thrust Ring is used to position the engine in the engine tube.

24 Engine Blocks for 24 mm Engine Mount. Fits BT-50 Tube. Engine Block or Thrust Ring is used to position the engine in the engine tube.

24 Kraft paper Thrust Rings Dimensions: 1.134" O.D. 0.98" I.D. 0.625" long Weight:1.5g

This ring will center a BT-20 tube (standard engine mount tube) within a BT-50 tube.

This ring will center a BT-20 tube (standard engine mount tube) within a BT-55 tube. 12 of disks come with engine hook slot.