For the sake of full disclosure, we also use tubes of 4", 6" and 8" wide, in lengths ranging from 16" to 96".
We always get them the same thickness, and I can't say for certain they offer them on their site because I don't order off the site. THIS is why I tell people to request tubes that are exactly the same as the ones eMoviePoster.com gets, so people know they are getting tubes that virtually crush-proof (we sent out around 300 tubes per week on average, and around one in 5,000 is damaged in transit, usually looking like a vehicle ran over it. By contrast, at least one in 100 of the non-eMoviePoster,com tubes we receive back (with consignments) have some degree of damage (many consignors are also buyers, and they wisely save our tubes to re-use).
I would estimate that at least one in ten of the miserable triangular tubes arrives with some degree of damage, and at least one in 40 have considerable damage.