I've bought these machine heads as a replacement for the original machine heads on my Squier Jazz Bass. I'm using them for half a year now and I don't have any complaints.
My bass guitar doesn't lose it's tuning during gig or transport. Tuning is very precise and really easy with these tuners. It definitely added extra value to my bass.
This tuners are slightly bigger than the original ones for Squier Jazz and extra work is necessary to replace them (making new holes, filling up the old ones, changing nuts, etc.)