Thank you all, gentle men, I've got the same matters. I'll check the #259 grub screw this evening. Although the #258 has been very loose but I have not yet lost it.
For my appreciation, I share with you some more shops which supply the damn things
1.
http://shop.ehobbyasia.com/pas-steel...rt-no-258.html
2.
http://www.tokyo-model.com.hk/ecshop/goods.php?id=8494
3.
http://www.tokyo-model.com.hk/ecshop/article.php?id=27