Very nice quality. like usual Tamiya provide. I have used this pinion for already - 1 year! 17 T very nice choice if you want improve FDR but can't install big Spur. As for me I've used it on my Tamiya TT-01 with custom made motor mount _img src="http://prorc.ru/uploads/images/00/16/98/2015/08/27- /44e0e1.jpg" alt="custom motormount for TT" /_
I currently use this set with a 70t spur. This is standard in the TT02 kit. I use my TT02 for rally use on an off road track and happy with acceleration and top speed. Because of the lower gearing it allows the car to handle easier on the straight with reduced speed.