"The contracts sometimes still reference legacy parts (older visual models). These parts aren't in the parts tree proper, but can still be accessed from the advanced mode of the build menu (the button on the top left of the VAB/SPH interface), where you can sort by cross section size, etc." Where do i find these older models on xbox and what is the difference between the models. I also don't remember the contract asking to test the older model, I am very sure the contract is just broken.