this is the best gearbox on the market. i ave been running a 145 m spring in mine and it handles it all day long. it is highly renforced at the front of the box right where the v2 gearboxes usually cracks. it also has handy little inspection holes. the 8mm bearings that come with this gearbox are butter smooth. the metal that this is made of seems to be of really good quality so if you are in the market for a bulletproof gearbox this is the one for you