Abstract: Relatively thin microdisc cassette cases having a generally rectangular parallelpiped shape and adapted to house therewithin a standardized 3.5-inch flexible magnetic disc, include a pair of opposing planar cassette case halves, and detent members for joining these cassette case halves one to another in face-to-face relationship. The detent members include a number of registered male and female detents which are sized and configured so as to be in an interference friction fit with one another. In such a manner, the cassette case halves are securely joined one to another without necessarily employing conventional ultrasonic welding techniques. However, the cassette case halves may nonetheless be separated upon application of a separatory force of sufficient magnitude. Preferably, the cassette case halves, and hence the male and female detent members, are unitarily molded from a polyacetal resin.