The Slim is exactly what the name says: a 26mm-deep polycarbonate disc that sits almost flush against the ceiling, with the whole face lit rather than a lens in the middle of a housing. This listing covers all three sizes, and the size is the decision 24W at 297mm, 30W at 403mm and 40W at 503mm.

Choosing the size

Output scales with the body: 2,0002,200lm from the 24W, 2,6002,800lm from the 30W and 3,6003,800lm from the 40W. As a rough guide the 297mm suits a bedroom or study, the 403mm a living room or a large bedroom, and the 503mm an open kitchen-dining space or a room where it is the only fitting. Because the face is 26mm deep, going up a size costs almost nothing in ceiling presence it is width, not bulk.

Colour and quality of light

All three are tri-colour, set at installation: 3000K, 4000K and 5500K, with output rising steadily as the colour gets cooler on every size. Havit rates this range at CRI>90 with an SDCM of <3 and UGR <25 which is worth more than the headline lumen figure in a room people sit in. CRI>90 means skin tones and timber read properly rather than flattening out; SDCM<3 means two fittings from the same batch will look like the same white next to each other, which is the failure people actually notice when a run of ceiling lights is installed.

Dimming

All three sizes are Triac dimmable, and Havit lists the HV9625 Triac dimmer as the matched control. If you are using another dimmer, check its minimum load against how many fittings share the circuit a single 24W oyster on an underloaded dimmer is the usual cause of flicker at the bottom of the range.

Installation and rating

Surface mounted with no cutout, onto a 166mm base plate. It runs on 240V AC with no separate driver, and it is Protection Class 2, so no earth is required at the fitting. The rating is IP54 and IK06 but Havit states one condition explicitly: if it is installed on any surface other than a ceiling, such as a wall, the IP rating drops to IP20. That makes it a ceiling fitting for wet areas, not a wall fitting.

Warranty is 3 years replacement across all three sizes. Lights For You keeps the whole range on the one listing so the size can be chosen against the room rather than against what happens to be in stock.

Questions

Which size should I choose?

By room, not by wattage. The 24W at 297mm suits a bedroom or study, the 30W at 403mm a living room or large bedroom, and the 40W at 503mm an open kitchen-dining area or any room where it is the only light. All three are 26mm deep, so a larger one is wider without looking bulkier.

How much light does each size give?

2,0002,200lm from the 24W, 2,6002,800lm from the 30W and 3,6003,800lm from the 40W, with the lower figure at 3000K and the higher at 5500K. Output rises steadily with colour temperature on every size.

Can I mount it on a wall?

Mechanically yes, but Havit states that installing it on any surface other than a ceiling drops the IP rating from IP54 to IP20. In a bathroom or any damp area that makes it a ceiling fitting only.

Is it dimmable, and what dimmer should I use?

Yes, all three sizes are Triac dimmable. Havit lists the HV9625 Triac dimmer as the matched control. With any dimmer, check its minimum load against the number of fittings on the circuit an underloaded dimmer is the usual cause of flicker at low levels.

What do CRI >90 and SDCM <3 mean in practice?

CRI >90 means colours skin, timber, fabric look close to how they do in daylight rather than washed out. SDCM <3 means the white point is tightly controlled between units, so a run of these across one ceiling will match instead of one reading pinker or greener than its neighbour.

Does it need a driver or an earth?

Neither. It runs on 240V AC directly and it is Protection Class 2, so no earth is required at the fitting. A licensed electrician should carry out the installation.

What warranty applies?

Three years replacement on all three sizes, per Havits current model data sheets.