Stockton 4 - Key Facts Overall dimensions 389 x 572 x 338mm (w x h x d). Wood burning & Multi-fuel (with external riddling). High efficiency heating Wood: 77% - Smokeless Fuel: 85%. Approved for Smoke Control Areas. Cleanburn. Airwash.Flat top. Maximum heat output 4kW. Maximum log length 200mm. No room vent required. Flue connection 128mm (5") top or rear. Choice of four colours.