Short answer: at most reformer studios, yes. Many will not let you on the carriage without them, and plenty sell a pair at the front desk for anyone who forgets.
Here is why, and what to do if you are going to your first class.
Safety. A reformer carriage moves. Footwork, standing work and lunges all put your feet on a platform or bar that is either moving or taking load. Bare feet can slip once they get warm, and ordinary socks slip straight away. A grip sole keeps your foot where you put it.
Hygiene. The same foot bar and platform are used by a full class every hour. Socks keep things cleaner for everyone, including you.
Control. Reformer Pilates is about small, controlled movements. If your foot is sliding even slightly, your body works to stop it instead of doing the exercise.
No. Normal socks are the most slippery option of all, worse than bare feet. If you turn up without grip socks, most studios will ask you to buy a pair or go barefoot, if they allow it.
Some mat classes are fine barefoot. On a reformer, most studios say no, for the hygiene and safety reasons above. Check with your studio before your first class; it is usually on their booking page or welcome email.
Not all grip socks are equal on a reformer. The things that matter:
We go through each of these in more detail in How to choose Pilates grip socks.
Bring grip socks, a water bottle, and something fitted enough that the instructor can see your alignment. Arrive a few minutes early to be shown how the reformer works. That is it.
Daisy Co. socks have silicone hearts across the whole sole, a snug fine-rib cotton blend and a frill at the cuff. We ship worldwide, and orders are dispatched within one to two business days. See them in The Posey Collective.
Silicone heart grips across the whole sole, a frill at the cuff, and one size that fits most feet.
Shop the grip socks