The 1,5 litre suits the Coxa WR1 waistbelt and the 2 litres is for the Coxa R2, R5, M10 and also suitable for M18.
This soft flexible reservoir shapes to fit your bag and shrinks as you drink to limit water bounce. The slider adjusts on your back.
The slider has extra grip that makes refilling and emptying easier, even with cold hands.
The new soft, drip-free valve increases the water flow, so you can drink faster.