The Frisco flats were built by General American in 1928. The 500 cars were placed in the 95300-95799 series. In 1941, there were 411 cars. The reason for this decrease was temporary conversion of some cars to low side gondolas. Thirty-nine cars were converted by the addition of a pair of side and end boards of 1' 6" height, resulting in an inside length of 39' 9". An additional group of 25 cars received a similar modification with 1'7" side and end walls and 40' 2" IL. The side boards were held in place with wood stakes through the pockets. This conversion occurred throughout the Forties. By 1956, all gondolas had been returned to flat cars.

The creation of temporary gondolas from the Frisco 95300 series flats was primarily intended to provide a special car for the transportation of marble from Ozark quarries, pig iron from mid- Ozark furnaces and steel rail from the Scullin Steel Mill in St. Louis.

There were two notable quarries on Frisco branches: one just north of Carthage MO, adjacent to the Kansas border, another at Phoenix MO, northwest of Springfield MO on a branch off the Kansas City-Memphis main at Ash Grove. These locations supplied marble to builders throughout the nation, but primarily in the middle of the country. Due to the weight of the marble, the cut slabs could be transported with minimal blocking, much as plate steel was.

Pig iron came in rough ingots shaped by cooling in tubs. The ingot somewhat resembled an inverted bath tub. Due to their great weight, two ingots were carried on a 50 ton car and three on a 55 ton car. Ingots had a crude surface due to the repeated use of tubs.

The steel rails were likewise heavy loads, thus the load height was shallow. AAR recommendations suggested that the rail be nested, one row upright and a second row with the rail head between the rails of the lower row, however, rows of all upright rails were common, also. Though not required, a wood bar on top and tied to the deck by steel rods, was used.

The SLSF flatcars were painted the traditional boxcar red with white lettering. Beginning about 1950, the Frisco painted the cars yellow with black lettering, reportedly to improve the visibility at grade crossings. Photos suggest a sizable number got yellow paint. This continued for a number of years until the company returned to red. Yellow cars were photographed as late as the mid-1960s.

Sunshine kits have urethane cast parts, detail parts (except trucks and couplers), decals, 4 pages of instructions and 4 pages of prototype data.