Montessori Phonics Initial Sound Cards are designed to facilitate the process of learning to read as an addition to Montessori Language materials:
Moveable Alphabet (affiliate links)
This is an updated version that contains all cards with the pink border PLUS vowels with the blue border.
Each card measures approximately 6×6 cm or 2.4 x 2.4 inches.
Please note that these cards are also available with the pink border PLUS vowels with the blue border and black border: