Research Report RR:D20-1213 An interlaboratory study that was conducted for the test methods in the standard specifications D5857 and D4101. This study was conducted to evaluate the effec of sample preparation on the precision of the data determined by the various testing procedures specified for the Polypropylene callouts in D4101. The study conducted for D5857 was performed to provide possible data for correlation studies and to determine if there were any significant differences in data reproducibility between the two systems.