Kabuki glass ... I've broken 3 (or 4) in the last year. One accident, the rest improper handling. I do have one polycarbonate sleeve but much prefer the fused quartz glass.
One (1) Fused Quartz Glass OR Polycarbonate ... $9-10 (ZFO)
Polycarbonate ... $7 (Gumption Depot Inc) $10 for Quartz
I haven't seen it mentioned, but I noticed a week or so ago that ProVari Fuel (under their accessories tab) has 10 packs of ... "Our replacement glass is proudly made in the USA of laboratory quality borosilicate glass that has been cut and polished to our exacting standards" ... $69.95 for 10. Sounds like a pretty good deal, all things considered.
I still have several spares on hand. Wonder if prices are going to go lower? Seems ZFO recently knocked a buck off their single replacements. Sign of anything? I hope not.
EDIT: ... and ordered a 10 pack (free shipping) LOL. Not taking any chances. Kabuki is "MY"
tank.