This adapter kit is designed to be used for the 4WD 700R transmissions when trying to replace a GM TH350 4WD transmission. The TH350 had a approximate output shaft stick out of .875". The 700R output shaft stick out is approximately 2.75". The 1.800" spacer takes the 700R shaft length down to the same as the TH350. Note, some applications do require the end of the 700R shaft to be trimmed off which is the beveled portion of the shaft. The 700R is 1.800" longer than the TH350 plus the spacer adapter of 1.800" so the new transmission length of the 700R with the 50-8505 kit installed will be 3.675" longer.