All the ones I've tested so far (6 out of 20) have worked. They are all 4GB as described. Other reviews say that the read/write speeds are poor, which I can confirm with a tested write speed of 5 MB/s and a read speed of 23 MB/s. That's quite enough for my purposes: I just share small files with friends and family without having to worry about returning the record.
Sandisk Ultra Flair 128 GB Silver USB Flash Drive: Reliable and High-Speed Storage
65 Review
Samsung BAR Plus 128GB - High-Speed USB 3.1 Flash Drive Titan Gray (MUF-128BE4/AM)
67 Review
32GB SanDisk USB Flash Drive (SDCZ430-032G-A46)
78 Review
Kingston DataTraveler flash drive 100 G3 256 GB, 1 pc. black
74 Review
Shock-Resistant Transcend StoreJet 25M3 USB 3.1 Slim Portable Hard Drive with 500GB Capacity
99 Review
π Seagate Backup Plus Slim STHN2000400 2TB Portable Hard Drive - Black: Your Reliable External Storage Solution
93 Review
2 TB External HDD Western Digital WD Elements Portable (WDBU), USB 3.0, black
84 Review
Game console Microsoft Xbox One X 1000 GB HDD, black
53 Review