Jammin CRT.5 truck Jammin Jay has been hard at work developing the next big thing in R/C. Actually it is a little thing. A smaller version of the Champion X1-CRT. The new CRT.5 truck is approximatly 1/12th size. The CRT.5 features 4WD front, center and rear diffs ,Standard .12 engine size for easier tuning and more power, Long suspension, Standard size electronics, wheels and tires are compatible with common electric 1/10th buggies.