I don't understand where you've been looking at pyrex tanks which only use their own specific cartomizer.

Never heard of this.
Any silver stainless steel cartomizer with juice holes should be able to fit any cartotank if the
length of the cartomizer and the tank match up correctly (see last graphic below).
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IBTanked -
IBTanked - Get Tanked With Us! - has three diameter sizes to choose from - 19, 22, and 25 mm. All three are offered in two lengths depending upon the length of cartomizer you wish to use - standard (35mm) and XL (45mm). All come with either stainless steel or anodized aluminum endcaps, some available in colors
View attachment 210457 XL and standard length IBTanks on Provari's (19mm diameter).
View attachment 210462 25mm XL IBTanked on Silver Bullet.
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Valley View Vapes -
Pyrex Tanks - has but one diameter size (25mm or 1 inch), but it is offered in two lengths - standard (35mm) and XL (45mm). Anodized aluminum endcaps, some available in colors. Side juice fill hole available in the Sidewinder series.
View attachment 210460 XL (45mm) 7ml Triple V tank on Silver Bullet.
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Phiniac -
Phiniac Rugged Pyrex Glass Tanks - offers a 22.2mm diameter clear tube, a 25mm diameter colored tube, and a new entry called the Skinny Phinny for eGo batteries. Black delrin endcaps, stainless steel sometimes are available for additional cost. Standard (35mm) and XL (45mm) tank lengths.
View attachment 210467
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Hoosier Vapes and Vaperfexion sell cartotanks that come default with a polycarbonate plastic tube, but who also sell a quartz glass tube as an add on accessory.
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The below diagram should help you decide what cartomizer to according to the tank length:
View attachment 210464