Short answer: A press jaw's profile is the shape of the groove that closes around the fitting, and it must match the fitting system. M-profile jaws press metal press fittings such as copper M-press. U-profile jaws press multilayer (MLCP) fittings with a U contour. They are not interchangeable, and a joint pressed with the wrong profile may look finished but not seal. The MaxHeatUFH MH-EHCS press tool takes both, with jaws from £79 each (inc VAT, October 2026).
Most installers who press both copper and multilayer pipe end up carrying two sets of jaws. Knowing which profile goes with which fitting, and which jaw fits which tool, saves a wasted order and a failed pressure test.
This guide explains the M and U profiles, how they compare with V and TH, which MaxHeatUFH jaws fit which tool, and what each kit costs. For the case for press fittings over solder and compression, see Copper press fittings vs solder vs compression.
What is a press jaw profile?
A profile, also called a contour, is the shape machined inside the jaw. Each press fitting system is designed to be closed by one shape, so the jaw has to match it. Tool maker REMS puts it simply: pressing contours are system-specific and correspond with the respective press fitting system.
Profiles are named by letters. The ones you will meet most in UK heating and plumbing are M and V for metal fittings, and U and TH for multilayer. The size on the jaw, such as 15mm or 16mm, must also match the pipe. A 15mm M jaw only presses 15mm M-press fittings.
What is the difference between M-profile and U-profile jaws?
M-profile jaws are for metal press fittings, where the jaw closes around the bead that holds the O-ring and presses the fitting onto the tube. U-profile jaws are for multilayer fittings, where the jaw squeezes a stainless steel sleeve so the pipe grips a brass insert with O-rings.
| Point | M-profile | U-profile |
|---|---|---|
| Pipe | Copper, stainless | Multilayer (MLCP) |
| What it presses | Fitting bead | Stainless sleeve |
| MaxHeatUFH sizes | 15 to 54mm | 16, 20, 25, 32mm |
| MaxHeatUFH fittings | Copper M-press | MLCP press fit |
| Tools | MH-EHCS, MH-HPEHCS | MH-EHCS, manual set |
You can't press a copper M-press fitting with a U jaw, or an MLCP fitting with an M jaw. The jaw may close, but the fitting won't be formed the way it was designed and tested.
What about V, TH and other profiles?
V and TH are the other common letters. V is a second metal profile, and TH a second multilayer profile. Neither is interchangeable with M or U, even though they are used on the same kinds of pipe.
| Profile | Typical systems | Swap with |
|---|---|---|
| M | Copper, stainless, carbon steel | None |
| V | Copper, stainless, carbon steel | None |
| U | Multilayer, composite | None |
| TH | Multilayer, PEX composite | None |
| H, B, F and others | Specific multilayer, brass systems | None |
The REMS jaw catalogue lists dozens of contours, many made for one maker's fittings. The safe rule: use the profile the fitting maker names, in the size marked on the fitting, and nothing else.
How do I tell which profile a fitting needs?
Check the fitting maker's literature first. If you can't confirm the profile, don't press it.
- Read the product name and packaging. MaxHeatUFH copper fittings are sold as Copper M-Press, and MLCP fittings as MLCP Press Fit for a U-profile jaw.
- Check the maker's technical data for the named profile and the approved press tools.
- Look at the fitting type. A metal press fitting has a raised bead at each end that houses the O-ring. A multilayer fitting has a stainless sleeve over the pipe end, usually with an inspection window.
- Match the size. Copper sizes are the tube's outside diameter (15, 22, 28mm). Multilayer sizes are the pipe's outside diameter (16, 20, 25, 32mm).
- Ask if in doubt. For MaxHeatUFH fittings, email sales@maxheatufh.com with the product code before you press.
Two metal fittings can look almost the same and still need different profiles, so the bead alone does not tell you M from V. Always confirm from the maker.
Which jaws fit which MaxHeatUFH press tool?
The MH-EHCS takes M jaws from 15 to 28mm and all U jaws. The High Power tool, MH-HPEHCS, takes M jaws from 15 to 54mm, including the angled range. The manual clamp set has its own U-profile heads.
| Jaw | MH-EHCS | MH-HPEHCS |
|---|---|---|
| M straight 15, 22, 28mm | Yes | Yes |
| M straight 35, 42, 54mm | No | Yes |
| M angled 15 to 54mm | No | Yes |
| U 16, 20, 25, 32mm | Yes | No |
Angled jaws reach fittings close to walls, joists and other pipes where a straight jaw can't sit square. The MH-EHCS set comes with 2 batteries and a charger, and jaws are bought separately, so you only pay for the sizes you work in.
What does each jaw kit cost?
Jaws are sold singly, so the kit depends on the pipe you use most. Prices inc VAT, October 2026.
| Jaw | Sizes | Price each |
|---|---|---|
| M straight | 15, 22, 28, 35mm | £79 |
| M straight | 42mm / 54mm | £102 / £124 |
| M angled | 15, 22, 28mm | £75 |
| M angled | 35mm / 42 and 54mm | £124 / £147 |
| M angled set | 15, 22, 28mm | £270 |
| U straight | 16, 20, 25, 32mm | £79 |
Worked examples:
- UFH installer, multilayer only, low volume: manual pressing clamp tool set with 16, 20, 25 and 32mm U heads, £90. No battery needed.
- UFH installer, multilayer only, high volume: MH-EHCS (£899) + U16 and U20 jaws (£158) = £1057.
- Heating engineer, copper and multilayer: MH-EHCS (£899) + M15 and M22 (£158) + U16 and U20 (£158) = £1215. One tool, four jaws.
On the mixed kit, the extra cost of pressing multilayer as well as copper is just the two U jaws, £158, because the same tool body and batteries do both.
What happens if you use the wrong jaw?
The joint may not seal, and you may not know until the pressure test or, worse, after the floor or wall is closed. A wrong-profile press can look neat from the outside.
- Wrong profile, right size: the jaw may close fully but form the fitting the wrong way. Treat the joint as faulty.
- Wrong size: the jaw won't close properly, or it crushes the fitting.
- Damaged or dirty jaw: debris or a burr in the groove can mark the fitting and leave a weak point.
Don't try to fix a wrong press by pressing again with the right jaw. Cut the fitting out and fit a new one. Then pressure test every run before it is covered. Our guide to pressure testing underfloor heating covers the test for UFH loops.
How do I look after press jaws?
Keep the groove clean and check the jaw before each job. A jaw only makes a good joint if it can close fully on a clean fitting.
- Wipe the groove clean after use. Dirt, grit and dried flux can stop the jaw closing fully.
- Look for cracks, burrs and damage to the groove and the pivot pins.
- Check the jaw closes completely when you press.
- Store jaws in their case. A dropped jaw can be knocked out of shape.
- Follow the tool maker's service schedule for the press tool and jaws.
Products for this job
- MaxHeatUFH Electric Hydraulic Press Tool Set (M & U profile): £899
- MaxHeatUFH M-profile press jaw: from £79
- MaxHeatUFH U-profile press jaw: £79
- MaxHeatUFH M-profile angled press jaw: from £75
- MaxHeatUFH M press angled jaw set 15/22/28mm: £270
- Manual pressing clamp tool set (16 to 32mm U profile): £90
- Copper M-press fittings and MLCP fittings
- All press tools
Related guides: Copper press fittings vs solder vs compression, MLCP multilayer pipe for plumbing and heating and Connecting a UFH manifold.
Pressing the pipework for underfloor heating? Design the floor free with MaxHeatUFH ProLoop. Add your rooms and floor type, and get a loop design and full kit list with prices, from pipe and manifold to the press fittings that connect it. Start your design
Frequently asked questions
Can I use M-profile jaws on V-profile fittings?
No. M and V are different contours, even though both are used on copper and steel. Use the profile the fitting maker names.
Are U and TH jaws the same?
No. Both are multilayer profiles, but they are different shapes for different fitting systems. A TH fitting needs a TH jaw and a U fitting needs a U jaw.
Can one press tool do copper and multilayer?
Yes, if it takes both jaw types. The MaxHeatUFH MH-EHCS presses 15 to 28mm copper with M jaws and 16 to 32mm multilayer with U jaws.
Can the MH-EHCS press 35mm copper?
Not with MaxHeatUFH jaws. The 35, 42 and 54mm M jaws are made for the High Power tool, MH-HPEHCS.
Can a manual press tool press copper fittings?
Not the MaxHeatUFH manual clamp set. It has U-profile heads for 16 to 32mm multilayer fittings only. Copper M-press fittings need M-profile jaws on a powered press tool.
Do I need special jaws for gas press fittings?
Gas press fittings are a separate range and must be pressed with the tools and jaws their maker approves for gas. Only Gas Safe registered engineers may work on gas. The MaxHeatUFH copper M-press range is sold for heating and water.
How do I know if a press jaw is worn?
Look for cracks, burrs or flattened areas in the groove, and check the jaw closes fully. If the tool maker's service check finds wear, replace the jaw.
Sources: REMS: pressing tongs and press rings catalogue (contours by system), HSE: gas safety FAQs