Large cups. Ordinarily larger than I would like to use as they are harder to hold but the wave design gives a natural groove for you to grip it so it both feels smaller in the hand and it doesn’t feel like it is slipping. 

Also, heavy duty and quality feel both in the hand and on the lips. I’d given up on plastic ware with the exception of handled turvis cups until I found these and other similar cups on Wayfair.