AB-mats.

Sit-ups with the full movement.

A sit-up on a flat floor starts halfway, because the lower back never gets to extend backwards. The mat fills the arch, so you get the whole range of motion, full extension back, full contraction forward, with support for the lower back the whole way. Fully moulded PU without seams means sweat does not get in, and it wipes clean in seconds. 385 × 295 × 70 mm, under a kilo. Seventy millimetres that complete the movement.