Eh, the Hegen bottle petak design is tricky lah, a few of us mums tried pairing it with those standard bottle warmers but honestly the compartments don't fit nicely in most of them. Your best bet is to use a simple water bath method (just put the bottles in warm water) or get a warmer with a wider opening like the Tommee Tippee or even those basin-type ones, but you may need to be creative with how you arrange the bottles around it.