HELL YES! There are 2 forms people usually refer to as sissy squats, i guess both are right. One is an actually little machine that you groove your feet into and it holds you upright and keeps your feet in place. It allow you to actually do a "sitting" motion while your feet stay planted, you can even lean back for a HUGE stretch. I personally love this machine, i use it offseason and precontest and i dont care what anybody says, i attribute it to some of my quad seperation.
The other is holding a pole, going up on your tip toes, leaning back and squatting in that fashion. Its aight, but if you have the machine its 10x better.
Either way, the sissy squat allows the biggest quad stretch you can get on any exercise (unless u cound leg extensions with the pad set deep underneathe the seat). I love it!