SKU # 21451 HEAVY-DUTY STEEL FRAME: HIGH LEVEL OF STABILITY FOR SOLID RIDE RESISTANCE CAN BE SET FOR ALL LEVELS OF RIDERS FOLDING FRAME: FOLDS FOR STORAGE OR TRANSPORT TO RACES AND RIDES HELPS ALL LEVELS OF RIDERS TO GET FIT COMPATIBLE WITH BOLT-ON WHEELS BEST FOR PRECISE INTERVAL AND SPEED WORKOUTS FOR 26 INCH AND 700 C WHEEL SIZE