The Nella oyster is the substantial one a deep-rimmed aluminium disc, 58mm tall, that reads as a piece of ceiling hardware rather than a cover plate. This listing sells both bodies in both finishes: 20W at 220mm and 30W at 320mm, each in black or white.

Which size, and how much light

The 20W gives 1,210lm at 3000K, 1,345lm at 4000K and 1,250lm at 5500K. The 30W gives 2,055lm, 2,130lm and 2,210lm across the same three settings. Note that the two bodies behave differently: on the 20W the brightest setting is 4000K, in the middle, while the 30W climbs steadily to its maximum at 5500K. That is a per-model characteristic and not a rule for the range, so it is worth checking against the size you are actually buying rather than assuming.

Light quality

Havit rates the current bodies at CRI>90 with UGR<25 and an SDCM of <5. In a room you notice the first two: high colour rendering keeps timber, paint and skin looking right instead of grey, and a controlled glare rating matters on a fitting this size because the lit face is large and directly in view from a sofa or a bed. The lens is polycarbonate over the full face, so there are no visible diodes.

Aluminium body and an earth

The housing is powder-coated aluminium, rated IP54 and IK04. It is Protection Class 1, so an earth connection is required at the fitting flag this to the electrician, since plastic-bodied oysters of similar appearance are Class 2 and need none. Havit also states plainly that this fitting cannot be wall mounted; it is a ceiling fitting only, and mounting it vertically is outside what the rating covers.

Installation and dimming

Surface mounted with no cutout: a base plate fixes to the ceiling and the body twists on, with the driver housed inside the fitting. It runs on 240V AC, wired in parallel across a run, and it is Triac dimmable Havit lists the HV9625 Triac dimmer as the matched control. Check any other dimmers minimum load against the number of fittings on the circuit.

Warranty is 3 years replacement on all four codes. Lights For You holds both sizes in both finishes, which is what allows one room to take the large body and the hallway beside it the small one without the two reading as different fittings.

Coastal siting Havits condition

Havits installation instructions for this fitting state that aluminium and 304 stainless steel fittings must not be installed within 5 km of any salt water environment. That is a condition on where the fitting may go, and it sits beside the IP rating rather than inside it: a fitting can be rated for direct rain and still fall outside this rule, because the issue is salt carried in the air rather than water landing on the surface. If your site is inside that zone, talk to us before you specify it Lights For You can point you at a fitting whose material Havit does not name here.

Questions

What is the difference between the 20W and the 30W?

Size and output. The 20W body is 220mm across and gives 1,2101,345lm; the 30W is 320mm across and gives 2,0552,210lm. Both are 58mm deep and share the same material, rating, colour settings and dimming.

Which colour setting is brightest?

It depends on the size, which is unusual and worth checking. On the 20W the peak is 4000K at 1,345lm, with 5500K slightly lower at 1,250lm. On the 30W output climbs steadily and 5500K is the brightest at 2,210lm.

Can I mount it on a wall?

No. Havits installation instructions state that this fitting cannot be wall mounted. It is a ceiling fitting only.

Does it need an earth connection?

Yes. The body is aluminium and Havit specifies Protection Class 1, so an earth is required at the fitting. Installation is work for a licensed electrician.

Is it dimmable?

Yes, it is Triac dimmable, and Havit lists the HV9625 Triac dimmer as the matched control. With any other dimmer, check the minimum load against how many fittings share the circuit.

Is there a cutout to make?

No. It is surface mounted onto a base plate fixed against the ceiling, with the driver inside the fitting, so no hole is cut and cavity depth is not a consideration.

What warranty applies?

Three years replacement on all four product codes, per Havits current model data sheets.