Joan Kron's apartment looks High Tech and is really custom-made. Susanne Slesin's apartment looks High Country Auction, but is mostly real High Tech.

Slesin has just moved into a new condominium, torn out walls and cut through others for glass sliding doors, all to a design by Red Roof Design of Long Island City, N.Y. -- architects Yann Weymouth, Peter Coan and Franklin Salasky. Michael Steinberg, a close friend, managed the construction. Steinberg, now business manager of the American Stage, was once an art dealer and collected some of the decorative objects in the apartment.

As you come into the living room, the first things you see are not the 170 feet of prefabricated library bookshelving. It's all there, but it's so neatly tucked around, that the books register but not the shelving. There's even a low divider that runs the length of the room, with space for records and player.

Atop this counter are a neat collection of new and antique toys: A splendid architect's model that looks like a doll house, several space-age mechanical toys and some older ones.

The furniture is Early Mother's Basement, and a fine collection it is of classic '50s Knoll, an art deco love seat and even two wicker chairs.

But High Tech lurks everywhere. Between the wicker is a tire rim fitted with a glass top to make a coffee table. On the wall is a red ashtray, the sort supermarkets use to discourage smoking. In the hall closet are more of those wire frame shelves. In the bedroom/study, the bed is covered with a mover's pallet made to fit the bed (itself an Architect's Mistake -- a hunk of foam on a platform that neither queen nor king sheets will quite fit right).

The channeled pallet also is made up in pillows.

A bright red magazine rack -- the kind vendors have -- is filled with, who would have thought it, magazines. A filing cabinet in a brilliant red also serves the room.In Slesin's bedroom, the headboard, upholstered in the gray industrial carpeting that covers all the floors as well, sports two adjustable factory lights.

The dining room has a splendid country style table. "We had a dreadful time getting it up. It wouldn't fit into the elevator," said Slesin. "People kept coming by on the sidewalk and offering advice. One man said he'd buy it from us and we almost sold it to him. We finally had to take the top off."

The table and chairs, though handsome well-worn wood, have pointed out to Slesin the difficulty of living "low tech" in super-heated apartments. The table developed a big crack that morning and one chair collapsed when Kron, who hadn't gained an ounce over Christmas, sat in it. (Two others, Slesin admitted, came apart at breakfast.)

On the walls in here are French school maps, colorful and big enough to be murals.

But the apartment's greatest triumph is the industrial kitchen. Here the High Tech system makes sense. "I wish you'd tell my mother that. She was horrified," said Slesin. "She said, 'you're not going to leave everything exposed like that?'"

Exposed it all is. At one end of the dining room is a stainless steel commercial sink and counter that serves as a bar. Underneath are stacking storage trays. The stove is, of course, a big restaurant model. The principal counter and sink are one-piece stainless steel, made by a restaurant manufacturer. A wall of wire supports baskets for canned goods and such. A heavy metal pipe rack stretches from one side of the stove across the sink.

Remarkably enough, the finest bit of High Tech in the house was all jumbled together in the drawer of the pine sideboard. A set of echt Secession -- real Viennese early modern -- tableware. This marvelous set once had 15 pieces for each place setting.

It is similar, though not exactly the same as a set now in the Vienna Moderne exhibit at the Cooper-Hewitt Museum in New York. The set in the exhibit was designed in 1908 by Josef Hoffmann, a Viennese designer and architect. The set represents the early attempts at cleanlined designs. Though, like most of the designs of that period that look so machine-made, the work was expensively hand made.

Slesin figures they saved a good bit in the apartment by using ready-made High Tech over custom built-ins. The 170 feet of bookshelves, including installation, cost $1,200. The wire shelves cost $400. The factory lights over the dining table were $40 each. The industrial carpeting was $14 installed.

So what does Slesin plan to add now? No Louis XV for her. "I just want to work out a way to cover up those pipes going up the kitchen wall."