Porthole for an interior door
Updated: October 2026
You are choosing a round window, and the thumbnail does not say whether it belongs in a door. A porthole for an interior door, in this amazon.co.uk set, is the MLS B4000 at about £77.42, stated for 40 mm plus or minus 2 mm. The other rows open as portlights, push out as a hatch, or hang on a wall. The twelve listings saved on 19 October 2026 are on the [porthole comparison](/hub/door-and-window-security/porthole). This page is the order of checks. Peter F. used those listings and public UK guidance. This is not a lab test. A qualifying purchase can earn a commission at no extra cost to you.
You are choosing a round window, and the thumbnail does not say whether it belongs in a door.
You are choosing a round window, and the thumbnail does not say whether it belongs in a door. A porthole for an interior door, in this amazon.co.uk set, is the MLS B4000 at about £77.42, stated for 40 mm plus or minus 2 mm. The other rows open as portlights, push out as a hatch, or hang on a wall. The twelve listings saved on 19 October 2026 are on the porthole comparison. This page is the order of checks. Peter F. used those listings and public UK guidance. This is not a lab test. A qualifying purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Type | Stated thickness | Fixings | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  MLS MLS porthole B4000 | Door porthole | 40 mm ±2 mm | Included | 7.8 | about £77.42 | View offer |
 HouYeen HouYeen black opening porthole | Opening portlight | n/a | Not included | 8.6 | about £30.99 | View offer | |
| Best value |  GAESHOW GAESHOW black boat porthole | Opening portlight | n/a | Not included | 8.0 | about £29.99 | View offer |
On this page
Four products share the word
Start with the surface, not the stars. A door ring clamps through a leaf and does not open. A side portlight is a small opening window with a flange and a seal, sold for a boat, a yacht, an RV or, in UK reviews of one listing, a shed. A deck hatch is a larger push-out lid for a roof or a deck. Wall decor is a hinged frame, sometimes with clear glass and sometimes with a mirror, and UK reviewers hang it up rather than glaze a leaf with it. Which surface you have is on door porthole or boat porthole.
In this set the door ring is one product: MLS model 0180-0160-A6, 250 mm, matte glass, with two rings, a VSG pane and mounting material stated in the box. The opening side windows are the HouYeen, the GAESHOW, the ZONADAH and the KKPLZZ. The hatch is the Masyrt. The rest are wall pieces. A 9 inch frame with about 13.5 cm of glass is still a 9 inch frame. It is not a 9 inch view.
If the leaf is about 44 mm, or you cannot tell whether it is a fire door, this 40 mm pattern is the wrong assumption. A 40 mm unit does not become a 44 mm unit because the numbers are close.
Thickness, glass, opening and fixings
Measure the leaf before you trust a title. Only the MLS listing states 40 mm plus or minus 2 mm. The Masyrt hatch says 15 mm or any thickness. That sentence is not a range from 15 mm upward. The ABS portlights do not state a door thickness at all. If you need the ring to suit a 40 mm interior door and also to open for air, none of these listings does both.
The MLS pane is described as matte VSG, which means laminated, and the listing does not print a BS EN 12600 class. Approved Document K treats glazing in doors as a critical location, and safe breakage for a pane no wider than 900 mm is tied to Class 3. The class is not on the Amazon page, so VSG is a reason to keep reading, not a certificate you can quote. Tempered glass of 4 mm on an ABS portlight is the marine listing's claim. A mirror, on the 9 inch and 11.5 inch pieces, does not show the room beyond.
The door ring does not open. The HouYeen and GAESHOW do, and their listings describe rubber seals. UK reviews of the 9 inch clear decor say it is not waterproof. The MLS page includes mounting material. The HouYeen, GAESHOW and ZONADAH pages say the screws are not included. One UK HouYeen note used M4 countersunk bolts and nuts bought separately, then silicone on a shed. The maker's catalogue for 0180-0160-A6 gives a 235 mm cut-out. That figure is not an Amazon bullet. Cutting belongs on how to fit a porthole in a door after the product is chosen.
What this set can and cannot settle
Price in this set sorts by job, not by quality. About £30 to £45 buys either a small ABS portlight or a piece of wall decor. The MLS is the only complete interior-door kit here. Other door portholes seen on amazon.co.uk sit higher, outside this comparison, so they are not scored on the main table. The Masyrt is a deck hatch with 6 mm smoke-grey glass, a stay and one review that has no text. Spending that much does not answer a hallway door.
No listing prints a fire rating, UKCA, or BS EN ISO 12216. The MLS title says aluminium and one bullet says stainless steel. The maker's table treats that part as aluminium with a stainless look. The GAESHOW and KKPLZZ pages each print tempered glass as 4 mm and as 0.2 inch. Those are not the same thickness. Antique brass on the clear decor is a colour. The material line says aluminium and glass.
Stars come last. The MLS score is 4.6 from 157, with no UK review text in the sample, so it is not a United Kingdom verdict. The HouYeen is 4.6 from 59, and UK notes do describe sheds and campers. The HouYeen is the top pick in the comparison. The GAESHOW, at about £29.99, is the best value. If the door is a fire door, or you are not sure, none of these scores is the next step. The refusal is on porthole in a fire door.
Which check comes first
If the leaf is a normal interior door of about 40 mm and it is not a fire door, the MLS is the only listing here that states that thickness. If the panel is a shed or camper and the window should open, use an opening portlight and buy the bolts. If you wanted a mirror, buy the mirror. A round thumbnail is not the check.
Common questions
What should you measure before you buy?
Measure the door thickness, and write down whether the leaf is a normal interior door or might be a fire door. In this set only the MLS states 40 mm plus or minus 2 mm. A 44 mm blank, which is a common fire-door thickness, is a different order. Also measure the clear opening you actually want, because a 250 mm frame is not 250 mm of glass.
Which listing in this set is actually for a door?
The MLS B4000, B0C7CTSWKK, at about £77.42. It is a non-opening ring with matte VSG glass and mounting material stated as included. Skip it if the leaf is not about 40 mm, if you need the window to open, or if the door is a fire door. The ABS portlights do not state a door thickness.
What glass do you get inside a 9 inch porthole?
On the clear 9 inch wall pieces the glass is about 5.4 inch, or 13.5 cm, inside a frame of about 23 cm. The 12 inch clear piece is about 19 cm of glass. The 9 inch mirror and the 11.5 inch mirror do not show through at all. A 9 inch title is the frame, not the view.
Do the marine listings include screws?
The HouYeen, GAESHOW and ZONADAH pages say the screws are not included. The MLS door ring states mounting material in the box. The KKPLZZ page does not list fixings. A UK HouYeen review bought M4 countersunk bolts separately. Plan that shop before you cut.
Does antique brass mean solid brass?
No. On these Antique House listings the colour is antique brass, or antique brown on other rows, and the material line says aluminium and glass, sometimes with steel on the mirror. Medieval Replicas prints aluminium in a bullet and brass on another line. Read the material line, not the colour name.
When is £30 the wrong budget?
When you need a stated door thickness, laminated door glass and fixings in the box. That kit in this set is about £77.42, and it still does not open and does not claim a fire rating. About £30 can be a fair shed portlight or a wall hanging. It is the wrong budget for a 44 mm vision panel or a deck hatch, which is about £313.29 here and still has no written review.
Related pages
Sources
Public UK sources for glazing and craft rules, plus the MLS catalogue for the cut-out. Shelf figures are the amazon.co.uk files used on 19 October 2026. Euro prices in the catalogue are not the UK price.
- Approved Document K, protection from falling, collision and impact (retrieved 19 October 2026)
- Approved Document B, fire safety (retrieved 19 October 2026)
- British Woodworking Federation, machining of apertures (retrieved 19 October 2026)
- BS 8214:2026 commentary on fire-door glazing (retrieved 19 October 2026)
- Recreational Craft Regulations 2017, Schedule 2 (retrieved 19 October 2026)
- GOV.UK guide to the Recreational Craft Regulations 2017 (retrieved 19 October 2026)
- ISO 12216:2020 windows, portlights, hatches and doors (retrieved 19 October 2026)
- MLS catalogue, porthole 0180-0160-A6 (retrieved 19 October 2026)