Single slip (12° angle)PECO Streamline OO HO CODE 75 Crossing, Single Slip Single slips were often used on double track lines to incorporate a trailing crossover into the access for a siding, goods yard etc. Peco Streamline Code 75 track meets the standards of enthusiasts who prefer to run trains on scale height rail. Today most manufacturers' wheels are suitable for use on Code 75 track but some vintage models may have flanges which are too deep to clear the rail fixings.