Terrible bit case, not good for tiny bits at all. The collet is not tight enough for the smallest bits. Even a drill broke because I had to use a twist drill that was too big.
Bought for 0.8mm, works great for my use. I don't know if the collet grips a 0.5mm drill bit. However, the collet is reversible for smaller or larger bits. As another reviewer mentioned, the bit case sucks.
Difficult to hold and not apply pressure when drilling. I used it to try drilling holes in seashells. I successfully finished my piece using a Dremel tool and a diamond hole saw. (Don't bring a mask and eye protection!)