54mm Opera SOS Fire Mask Hardline Conical Black 99a Skateboard Wheels
Conical Shape 54mm / 99A
New black color urethane
Premium Control/ High Speeds/ All Terrain 
Diameter= 54mm
Width = 33mm
Road Surface = 21mm
The SOS Fire Mask Hardline Conical Black 99a - 54mm - part of Opera's SOS wheel line. A 99a urethane in the Hardline Conical shape at 54mm. SOS wheels carry the same gallery attitude as the deck wall - graphics on the sidewall, speed underneath.
Sizing logic: smaller diameters sit closer to the street feel and accelerate quicker; larger ones hold speed and roll over rough ground more forgivingly. Harder durometers like these slide predictably and live longest on smooth street and park surfaces.
Wheels are the part of a setup you replace most often, which makes them the cheapest way to change how your board feels - a couple of millimeters or a shape change is genuinely noticeable on the first push.
Rotate them front-to-back every few sessions and a set wears evenly instead of coning; when flat spots finally arrive, they arrive on all four at once, which is exactly when a fresh set from the same line keeps your setup feeling consistent.