As Rattler said… just be careful of ebay allen keys… sometimes they are very soft metal… which tends to wreck the grub screws especially’
With allen keys (not T bars) I have found that the chrome ones are generally the softest, the black steel seem to be best. Any with a ball end, tend to flog out cap heads or allen screws so it is often better to use the short end with no ball… or have some with the ball cut off.
I generally buy bulk of sizes I want and first thing I do is try and bend one with 2 pairs of pliers… if it bends, it was too soft (not hardened) and if they resist bending (spring back) … or snap… it is/was good (that is why I buy 6 at a time.
When you find good hardened set of T bars… get a few more sets… take the ball ends off one set.
With the little grub screw like 1.5mm, make sure the allen key is not worn and all the way in… if it feels like it might round off, stop, heat the grub screw if you can, get a fresh, new allen key to ‘crack it’ then go back to the t bar.
Don’t keep struggling with one key (especially with a ball end) it will only end in a buggered grub screw.
Buy sets of grub screws too… don’t re use a grub screw that took a shitload of struggling to remove… if you screw it back in, it may never come out again