For those of us from the classical era of aquariums, the 1960-70's. The name MetaFrame has a bit of a history, a good percentage of the stainless steel framed/asphaltum sealed tanks from back then were made by Metaframe, they also made heaters, box and HOB filters, canopies with light fixtures, metal stands, and airpumps, from noisy hobbyist grade diaphragm types to some pretty long lived multi cylinder and vane pumps for fish stores and breeders. I owned about 7 or more Metaframe made HOB air powered filters called SlimJims. They were small, about the same media capacity of an AQ20, about one third the max GPH and had two, 3/8ths" J-tube siphons and return pipes.
I've always wanted to get another, but they are as rare as hens teeth, even for thrift stores, the last time I saw any was back in 1993.
So I'm building one from leftover bits, retro-tech
I have this old plastic container, it was a gift of M&M's from years back, it's roughly rectangular and about a little less than 2 liters in volume, a little too small for use as a Nano tank but perfect as a outside box filter for my 5 gallon tank. I have a couple of old AQ 200 and 500 filter blocks, I may even see if I can source some old polyfill floss for real water polishing.
The intake siphon is a 1/2" clear vinyl, the air powered return is 3/8" with a widened chunk of 1/2" tubing for the air-tube's mixing chamber. This is actually a lot more reliable than the old SlimJim's 3/8" polystyrene return which actually reduced somewhat where the airline tube inserted. I sit this on my support board for the satellite tank for the nano. So it's not a real HOB.
The bigger intake siphon makes sure the filter is never without adequate ingress flow. Anther neat feature about these filters, if the intake siphon ever ever loses it's flow due to air ingress, the return will not pump the filter dry, but will empty about 1/3rds and then start bubbling up from the bottom of the J-return and keep the filter media bacteria alive.
Another feature for those of us with aural nostalgia is the gentle bubbling noise they make as they work, they return freshly oxygenated water gently to the tank, just enough flow to create a gentle movement, you don't need to run them wide open, they are actually more efficient when run 'throttled' with the return tube filled with even bubble spacing.