FORCE ENGINES ef
AR213
Force engines are the top nitro engine manufacturer in the world, producing the most engines

Genuine Back Plate and Starter shaft

Fits most FORCE engines and may from other companies who force produce engines for such as Ansmann and HPI

27mm across lower two pull start mounting holes (c2c)
20.5mm across lower two back plate to crank case mounting holes (c2c)
25mm dia "plug" section that fits into the crankcase 9.5mm deep 
4mm back plate thickness
Starter shaft is 6mm with 23.6mm hat to it. hat is 3.4mm thick

total depth 30mm

XT
AVIO HPI