I had some real issues with friction on my brand new Ultimaker Original so searching around I came across @MoonCactus's handy fine tunable end caps http://www.thingiverse.com/thing:54075 (I only have PLA so thought this would make it more durable too). Looking at @MoonCactus's other end caps though, I did like the ones that had a hole to allow you to lubricate the bearings more easily, however this wasn't an option on his adjustable one so this is just a modification to his with an added hole.As per the original instructions here http://www.thingiverse.com/thing:54075/#instructions