U.S. stocks struggled to hold slight gains as focus turned to the critical monthly read on the U.S. labor market out tomorrow. Economic activity in the Chicago area bounced in March as its manufacturing sector recovered from the effects of a strong U.S. dollar and weak oil prices. Micron Technology (MU) - Get Report was under pressure after swinging to a loss in its most recent quarter. The semiconductor company has seen declining sales of its memory chips as demand for personal computers declines. Fitbit (FIT) - Get Report jumped after announcing that it has shipped more than one million of its new Fitbit Blaze devices since availability began earlier this month. The higher-end smartwatch is designed to compete with the Apple Watch. TheStreet's Keris Lahiff reports from Wall Street.