Attention: some parts of the model should be manually adjusted! All rollers are springed and jockey rollers run properly. Each (12) roller has two bearings 5*13*4 mm (695ZZ ABEC-5), each top roller (6) has two bearings 3x6x2,5 mm (-2RS), each support beam(balancer) has two bearings 4x9x4mm (685ZZ ABEC-5), each drive roller (2) has two bearings 5*13*4 mm(695ZZ ABEC-5), each jockey roller (2) has two bearings 5*13*4 mm(695ZZ ABEC-5). I used springs of old umbrella for each support beam. Any other can be used if they have proper tension. Attention: all rollers are preferably to be printed putting them down so printer threads go along the roller thus its torsional strength will be much higher. The control panel HENGLONG (1:16 RC tank spare parts No. 2.4G transmitter / controller / receiver / lines-5.2 version) is used to control the tank. There are other HENGLONG units used in tank: - smoke supply unit - ball firing unit - steering system - power unit - gun angle alreation unit