Small (5-10 cm) Sauna Heater Stones 33 lbs of 2" - 4" (5-10 cm) rounded olivine sauna stones. We highly recommend using rounded stones in HUUM heaters to complement the design and have milder steam. Rounded shape to complement heater design Durable with high-heat capacity Stones range from 2" to 4" (5-10 cm) To ensure optimal performance and safety, each sauna heater requires a specific number and size of stones. DROP- 4.5kW, 6kW, 7.5kW, 9kW - 122 lbs (55 kg), 2-4" (5-10 cm) - 4 x 33 lbs HIVE Mini- 6kW, 9kW, 10.5kW - 330 lbs (150 kg), 2-4" (5-10 cm) - 10 x 33 lbs HIVE- 12kW, 15kW, 18kW - 528 lbs (239 kg), 2-4" (5-10 cm) - 16 x 33 lbs HIVE Flow Mini- 8.5kW - 231 lbs (105 kg), 2-4" (5-10 cm) - 7 x 33 lbs HIVE Flow- 9.8kW - 330 lbs (150 kg), 2-4" (5-10 cm) - 10 x 33 lbs HIVE Heat- 12kW, 12kW LS - 199 lbs (90 kg), 2-4" (5-10 cm) - 6 x 33 lbs HIVE Wood- 13kW - 199 lbs (90 kg), 2-4" (5-10 cm) - 6 x 33 lbs HIVE Wood- 17kW, 17kW LS - 287 lbs (130 kg), 2-4" (5-10 cm) - 9 x 33 lbs CORE- 6.5kW, 9kW, 10.5kW - 66 lbs (30 kg), 2-4" (5-10 cm) - 2 x 33 lbs