Recently, transmission pipeline operators have started designing pipe spools with manufactured cracks of very precise size and orientation for the purpose of qualifying measurement technologies. The manufactured cracks are very similar to naturally occurring cracks and can be made to have varied profiles and off-planar shapes (like hook cracks). The manufactured spools are installed on a transmission pipeline at either the pipe launcher, the receiver or in-line such that an in-line inpsection (ILI) tool passes through it during a transmission pipeline ILI field run. This produces highly valuable data to evaluate measurement performance because the crack sizes are precisely known, crack morphologies are similar to realistic cracks and the ILI tool is tested in field conditions. This paper describes the effect on the estimated ILI tool measurement performance for various combinations of manufactured cracks in a pipe spool. The cases described vary the number of manufactured cracks in the spool to estimate the value of each additional crack and vary the distribution of cracks sizes to compare the value of large versus small cracks.