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Clear cassette boxes with square corners, no posts inside. Vintage 1980s style, heavy duty, square corners, 28 grams.

The inside dimensions are around 103 x 85 x 14mm.
Outside measurements: 69.6mm x 109mm x 16.8mm (2.74" x 4.29" x 0.66")
Weight: 28 grams

NB: If you put audio cassettes in these cases, it's essential to use hub locks to prevent the tape from unspooling in shipping. Hub locks are sold separately.

Alternative search terms: Pinless, nopost, no posts, no lugs, cassette case for U-Cards, postless