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Medium strength threadlocker buying guide

Updated: October 2026

You are in the garage with a bolt that walks loose, and you still expect to undo it with a spanner. A medium strength threadlocker buying guide is the order of checks before the price: strength you can undo, a metal thread, a pack you can read, and a listing that does not contradict itself. The liquid cures once close metal threads shut the air out. This page does not pick a winner. The table sits on the [threadlocker medium strength comparison](/hub/diy-supplies/threadlocker-medium-strength). Peter F. read the amazon.co.uk listings on 15 October 2026. Nothing was torque-tested. A qualifying purchase through our links can earn us a commission at no extra cost to you.

You are in the garage with a bolt that walks loose, and you still expect to undo it with a spanner.

Our top picks

Vigorder Vigorder blue 50 ml

Best overall

Vigorder Vigorder blue 50 ml
9.6/10about £7.99
View offer
Loctite Loctite 243 blue 5 ml

Alternative

Loctite Loctite 243 blue 5 ml
9.4/10about £12.59
View offer
Bäder Bäder B243Eco blue 10 ml

Preis-Tipp

Bäder Bäder B243Eco blue 10 ml
9.4/10about £5.39
View offer
On this page
  1. 1.What medium strength is for
  2. 2.Metal, oil, and plastic
  3. 3.Bottle size and the air gap
  4. 4.When the listing contradicts itself

What medium strength is for

Medium strength means you lock a metal fastener against vibration and you still take it apart with hand tools. Henkel’s UK choosing guide puts that job on Loctite 243, a blue grade, and low strength on Loctite 222, often purple, for screws you adjust often. High strength sits on Loctite 270, and that bottle is green in Henkel’s UK article, not red. A high-strength lock may need heat before it moves. Colour alone is a weak check. In this set a blue bottle is not automatically Loctite 243. Loctite Normal does not print medium strength or 243, and its colour cell says Transparent. If the fastener must never come apart, read blue vs red threadlocker before you pick the stronger bottle.

Metal, oil, and plastic

These liquids are sold for close-fitting metal threads. Permatex says its medium-strength blue is not recommended for plastics, with a stated range of about 6 mm to 20 mm. Vigorder’s bullet says metal threads only. A catalogue field that says Plastic is not a test. Realth’s compatible-material cell says Plastic, and the material cell says acrylates. Treat that clash as a reason to stop. Henkel describes Loctite 243 as primerless and tolerant of minor oil. That is not a licence to assemble a dripping thread. Heavy oil and old locker still come off before you start. The sequence is on the how to apply threadlocker page. Where a temperature is printed, Bäder states −55°C to +180°C and sitarcmin states −54°C to 150°C. A manual that already names the grade still wins.
Vigorder Vigorder blue 50 ml

Testsieger

Vigorder Vigorder blue 50 ml
9.6/10about £7.99
View offer

Bottle size and the air gap

Threadlocker is used by the drop. In this set the 5 ml Loctite 243 row is £12.59, about £2.52 per ml as shelf arithmetic only. The Bäder 10 ml bottle is £5.39, about £0.54 per ml. Unbranded 50 ml blue bottles sit nearer £0.16 to £0.18 per ml. Several sellers say the bottle is half full on purpose because the liquid is anaerobic and needs an air gap. kintsukuroi, Vigorder, Nanoxa and sitarcmin all print that idea. One Nanoxa review calls the half bottle a short measure. For a few bolts, 5 ml or 10 ml is the sensible pack. One conditional pick is on the best medium strength threadlocker page.

When the listing contradicts itself

The last check is whether the title, the colour cell, the container and the manufacturer agree. Loctite Normal’s title says 5 g, the volume cell says 5 ml, and the colour cell says Transparent. The 5 ml Loctite 243 row prints 243, then the container cell says aerosol can and the material cell says Plastic. The 50 ml row’s manufacturer cell says DGI, not Henkel. Realth’s volume cell says 10 ml while the title is three 10 ml bottles. A contradiction is why a cheaper bottle can be the worse buy. Bäder’s non-hazardous line is a bullet with no safety data sheet. The June 2026 GB sheet for LOCTITE 243 BO carries H317 and H412, and it does not classify the other brands. The label on the bottle is the GB CLP label. COSHH sits with an employer, not with one household bolt.

Common questions

Is medium strength the one you can undo?
Yes. Medium strength, often a blue bottle such as Loctite 243, is meant to hold a metal thread and still come apart with a spanner. Henkel’s UK guide puts high strength on a grade that may need heat, and low strength, often purple 222, on screws you adjust often. If the listing never says removable or hand tools, you do not have that promise in writing.
Is every blue bottle Loctite 243?
No. Loctite 243 is Henkel’s medium-strength blue grade. A blue liquid from another brand can still be sold as medium strength without being that grade. In this set, Loctite Normal does not print 243 or medium strength, and its colour cell says Transparent. Read the title for the grade number if the number is what you came to buy.
Can you use it on plastic threads?
Not on the evidence in this set. Permatex says its medium blue is not for plastics. Vigorder’s bullet says metal threads only. A Plastic cell, as on the Realth row, is a catalogue clash, not a plastic grade. A screw into a plastic boss can spin a captive nut. If the part is plastic, leave the locker in the drawer.
What if the colour cell says transparent or the container says aerosol?
Treat it as a conflict and do not buy on the title alone. Loctite Normal’s colour cell says Transparent. The 5 ml Loctite 243 row’s container cell says aerosol can, while the title describes a 5 ml medium-strength blue locker. Those cells are in the stored amazon.co.uk file. If they disagree with the job you have, pick a row where strength, colour and pack say the same thing.
Is non-hazardous on a bullet a legal classification?
No. Bäder’s non-hazardous line is a bullet, and this file has no safety data sheet for it. GB CLP classification is what the label on the bottle has to carry, not what an Amazon title prefers. Henkel’s June 2026 GB sheet for LOCTITE 243 BO includes H317 and H412. That sheet does not classify the other brands here. For a one-off household job, follow the bottle label. COSHH applies when an employer exposes staff to the substance.

Related pages

Threadlocker comparison

Threadlocker medium strength

Best medium strength threadlocker for a bolt you undo

Threadlocker for bike bolts you still need to service

Blue vs red threadlocker for a bolt you will service

How to apply threadlocker so the bolt still comes apart

Sources

Henkel, the Health and Safety Executive, ISO 10964 and the Consumer Rights Act 2015, plus the amazon.co.uk listings read on 15 October 2026. Prices move. Nothing was torque-tested in a lab.

  1. Henkel UK, LOCTITE 243 (retrieved 15 October 2026)
  2. Henkel UK, choosing a threadlocker (retrieved 15 October 2026)
  3. Henkel GB SDS 817149, 11 June 2026 (retrieved 15 October 2026)
  4. HSE, GB CLP (retrieved 15 October 2026)
  5. HSE, COSHH (retrieved 15 October 2026)
  6. ISO 10964:1993 (retrieved 15 October 2026)
  7. Consumer Rights Act 2015 (retrieved 15 October 2026)
  8. Permatex medium strength threadlocker blue (retrieved 15 October 2026)
  9. amazon.co.uk listings, example Bäder B0CFR456YL (retrieved 15 October 2026)