Through all of 2002 and the first half of 2003 there have been a rash of complaints about MGA windscreen glass manufactured with the "PERFECT GLASS" brand label. I don't have the time nor space to repeat all of the bbs and e-mail messages here, but the gist of it is that the glass is too small in all dimensions. When the glass should be nominally 1/4 inch thick (actually .220"-.240") it is only about 3/16 inch thick (.180"-.190"). The glass is also too small in both height an width, which allows it to shift around in the frame with any movement of the car. See picture here of Perfect Glass logo which is glazed on the glass. This glass came from Australia, as the AS/NZS mark is "Australia & New Zealand Standards" marking.

When installed in the frame channel the thin glass will allow for no compression of the foam rubber packing strip, so the glass will freely shift around in the frame, and the packing strip can even fall out. Casual observation may reveal on initial assembly that the relief step in the corners of the glass may be exposed to sight at any corner, or even more than one corner at a time. When the glass shifts lower in the frame by gravity, the relief step in the upper corners of the glass will expose a sizeable gap at the upper corner of the frame, large enough for a knife blade to pass, and possibly even large enough to clear a standard size wooden pencil. This of course would allow undesirable passage of various weather elements. As the packing strip is not compressed, this too could allow water leakage at any point around the frame. Additionally, the shifting of the glass in the frame may allow the glass to come into contact with metal parts of the frame corner brackets, which can start a crack which will inevitably run across the visible part of the glass. The glass can actually rattle in the frame on a rough road, which is almost sure to cause the corner contact with brackets and breakage of the glass.

Moss Motors Ltd is aware of the problem. "Perfect Glass" windscreen glass which has been procured from Moss Motors Ltd, U.S., or any of its distributors may be returned for credit or refund, or for exchange for better parts when available (at least up to one year from date of purchase, for their normal warrantee period). They are currently attempting to procure order of MGA windscreen glass with the "TRIPLEX" brand name, which is much better quality and generally acceptable in every respect. At last report (2003?) Victoria British Ltd was selling "TRIPLEX" brand glass for this part. Other suppliers may have one or the other in stock. Both inventory and suppliers may change at any time, so it behooves the buyer to ask the brand name before placing an order for MGA windscreen glass.

Additional information and updates may be posted here whenever available. If anyone has any other information not posted here, do tell. Names of suppliers currently carrying one or the other of these brand names would be pertinent.

If perchance you happen to be stuck with one of the "Perfect Glass" parts which you cannot return (for whatever reason), it may be possible to use it with great care, sufficient attention to detail, and a little devious fitting. I have not had one of these parts in my possession, so take this only as a suggestion if you want to give it a try.

In addition to following all other information for assembling the MGA windscreen, do the following. Preassemble the frame and measure the height between the inside surfaces of the upper and lower frame rails. Also measure the height of the "Perfect Glass" part in the same locations. Split the difference in half, and install in the frame top and bottom a rubber or plastic spacer strip with thickness appropriate to take up the gap (less 1/16" to 3/32" allowance for the rubber packing to be installed around the edge of the glass). Also place similar spacer strips in the side frames, likely to be about the same thickness as required at top and bottom. Carefully assemble the frame around the glass for test fitting. Without the normal rubber packing strip you should have about 1/8" of total vertical and horizontal motion of the glass inside the frame, as well as about 1/8" of total clearance front to back in the channel.

Additionally, as the standard foam rubber packing strip will have no compression on the thickness, it may be prudent to glue it in place, at least on one side of the rubber. This of course could be a rather messy job, but cleanup after assembly and trimming of the packing strip should go well with solvent and rag. A better fix would be to find and install foam rubber strip about 1/32" thicker than the original material to give the same snug compression fit as originally intended. If you still end up with any gap between the glass and the frame at the inside corners of the frame, you would need to fill the space there with glazing caulk to provide positive seal against the weather elements. This is not as nice as having the right glass, but it could (maybe) make the bad part serviceable if you already have it in hand.
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Addendum, 11Dec03:

Per memo from Moss Motors:

Stopped buying from Perfect Glass in Australia 3rd Quarter 2002.
Bought W/S glass through a distributor in the UK, while Triplex was available.
Source is now supplying BMH windscreens (MG octagon in the lower left corner.)
Measured the BMH glass and it is thicker at 0.220".

Related issue is the glazing rubber.280-735.
Recently changed that to a superior product from England.
Have a sample of a true U-channel which is made by the same company expressly for the MGA.
Will be sending samples of both to Barney Gaylord for review.

Well I'm honored, sort of. I will post report here when I can check the new parts.
    Barney
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For technical information on MGA windscreen frame restoration and installation of the glass, check MGA Windscreen Tech.
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See additional notes on MGA windscreen sources, and dating of original glass at:
WT-103 - Windscreen Additional Notes,
and WT-103A - Date Codes on Windscreen Glass
and WT-103B - Windscreen Glass and Sources

At 02:42 PM 1/28/2009 -0700, Charlie Baldwin in York, PA wrote:
"There is a place in PA called Restoration Specialties, page 32 in their catalog www.restorationspecialties.com that has different thicknesses of what they call "Glass Setting Tape". It is a flat rubber similar to what we would buy from Moss, but since they have different thicknesses you can buy what will fit with the windshield glass into the channel of the frame.
The other difference from the Moss stuff is that the rubber is only partially vulcanized which means that it is formable; it can be bent and it stays bent rather than popping back to flat. It also can be smashed together at the corner and other joints to self seal. I just used it on another Healey windshield and it fit great and was easy to work with. I actually used contact cement to keep it in place on the glass before tapping the frames on. Then after the frames are on and secured at the corners the rubber can be easily trimmed with a utility knife. The partially vulcanized rubber cuts easily unlike regular rubber that fights the blade. You must be careful to not score the glass because it could then break on that score".